Examples with solutions for Using the Pythagorean Theorem: Using additional geometric shapes

Exercise #1

The rectangle ABCD is shown below.

BD=25,BC=7 BD=25,BC=7

Calculate the area of the rectangle.

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Video Solution

Step-by-Step Solution

We will use the Pythagorean theorem in order to find the side DC:

(BC)2+(DC)2=(DB)2 (BC)^2+(DC)^2=(DB)^2

We begin by inserting the existing data into the theorem:

72+(DC)2=252 7^2+(DC)^2=25^2

49+DC2=625 49+DC^2=625

DC2=62549=576 DC^2=625-49=576

Finally we extract the root:

DC=576=24 DC=\sqrt{576}=24

Answer

168

Exercise #2

Look at the square below:

444

Is the sum of the two diagonals greater than the sum of the 3 sides of the square?

Video Solution

Step-by-Step Solution

Let's look at triangle BCD, let's calculate the diagonal by the Pythagorean theorem:

DC2+BC2=BD2 DC^2+BC^2=BD^2

As we are given one side, we know that the other sides are equal to 4, so we will replace accordingly in the formula:

42+42=BD2 4^2+4^2=BD^2

16+16=BD2 16+16=BD^2

32=BD2 32=BD^2

We extract the root:BD=AC=32 BD=AC=\sqrt{32}

Now we calculate the sum of the diagonals:

2×32=11.31 2\times\sqrt{32}=11.31

Now we calculate the sum of the 3 sides of the square:

4×3=12 4\times3=12

And we reveal that the sum of the two diagonals is less than the sum of the 3 sides of the square.

11.31 < 12

Answer

No

Exercise #3

A cuboid has a width measuring 8 cm and a height of 4 cm.

Calculate the length of the side AC.

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Video Solution

Step-by-Step Solution

To find the length of the diagonal AC AC on a cuboid, we will use the Pythagorean theorem twice:

  • Step 1: Calculate AB AB , the diagonal of the face of the cuboid:

We assume the cuboid's known dimensions, with width 8cm 8 \, \text{cm} and height 4cm 4 \, \text{cm} . Assume l l for one dimension along the base.

Since AB=w2+l2 AB = \sqrt{w^2 + l^2} , solving for AB means understanding both directions. As the length isn't given, we solve specifically for vertically so AC AC depends on full volume space:

  • Step 2: Calculate diagonal AC AC :

AC=AB2+height2=82+42=64+16=80cm AC = \sqrt{AB^2 + \text{height}^2} = \sqrt{8^2 + 4^2} = \sqrt{64 + 16} = \sqrt{80} \, \text{cm}

In this way, we determine the length of diagonal AC AC is 80 \sqrt{80} cm.

The correct choice corresponding to this calculation is Choice 3: 80 \sqrt{80} cm.

Answer

80 \sqrt{80} cm

Exercise #4

The trapezoid ABCD and the rectangle ABGE are shown in the figure below.

Given in cm:

AB = 5

BC = 5

GC = 3

Calculate the area of the rectangle ABGE.

555555333AAABBBCCCDDDEEEGGG

Video Solution

Step-by-Step Solution

Let's calculate side BG using the Pythagorean theorem:

BG2+GC2=BC2 BG^2+GC^2=BC^2

We'll substitute the known data:

BG2+32=52 BG^2+3^2=5^2

BG2+9=25 BG^2+9=25

BG2=16 BG^2=16

BG=16=4 BG=\sqrt{16}=4

Now we can calculate the area of rectangle ABGE since we have the length and width:

5×4=20 5\times4=20

Answer

20

Exercise #5

Using the rhombus in the drawing:

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Calculate the area?

Video Solution

Step-by-Step Solution

Remember there are two options to calculate the area of a rhombus:

1: The diagonal multiplied by the diagonal divided by 2.

2: The base multiplied by the height.

In the question, we are only given the data for one of the diagonals and one of the sides, which means we cannot use either of the above formulas.

We need to find more data. Let's begin by finding the second diagonal:

Remember that the diagonals of a rhombus are perpendicular to one another, which means that they form a 90-degree angle.

Therefore, all the triangles in a rhombus are right-angled.

Now we can focus on the triangle where the side and the height are given, and we will calculate the third side using the Pythagorean theorem:

a2+b2=c2 a²+b²=c² Insert the given data:

32+x2=52 3^2+x^2=5^2 9+x2=25 9+x^2=25 x2=259=16 x^2=25-9=16 x=16=4 x=\sqrt{16}=4

Now that we have found the second half of the diagonal, we can calculate the area of the rhombus by multiplying the two diagonals together.

Since the diagonals in a rhombus are perpendicular and cross each other, they are equal. Hence, our diagonals are equal:

3+3=6 3+3=6 4+4=8 4+4=8 Therefore, the area of the rhombus is:

6×82=482=24 \frac{6\times8}{2}=\frac{48}{2}=24

Answer

24

Exercise #6

The trapezoid DECB forms part of triangle ABC.

AB = 6 cm
AC = 10 cm

Calculate the area of the trapezoid DECB, given that DE divides both AB and AC in half.

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Video Solution

Step-by-Step Solution

DE crosses AB and AC, that is to say:

AD=DB=12AB=12×6=3 AD=DB=\frac{1}{2}AB=\frac{1}{2}\times6=3

AE=EC=12AC=12×10=5 AE=EC=\frac{1}{2}AC=\frac{1}{2}\times10=5

Now let's look at triangle ADE, two sides of which we have already calculated.

Now we can find the third side DE using the Pythagorean theorem:

AD2+DE2=AE2 AD^2+DE^2=AE^2

We substitute our values into the formula:

32+DE2=52 3^2+DE^2=5^2

9+DE2=25 9+DE^2=25

DE2=259 DE^2=25-9

DE2=16 DE^2=16

We extract the root:

DE=16=4 DE=\sqrt{16}=4

Now let's look at triangle ABC, two sides of which we have already calculated.

Now we can find the third side (BC) using the Pythagorean theorem:

AB2+BC2=AC2 AB^2+BC^2=AC^2

We substitute our values into the formula:

62+BC2=102 6^2+BC^2=10^2

36+BC2=100 36+BC^2=100

BC2=10036 BC^2=100-36

BC2=64 BC^2=64

We extract the root:

BC=64=8 BC=\sqrt{64}=8

Now we have all the data needed to calculate the area of the trapezoid DECB using the formula:

(base + base) multiplied by the height divided by 2:

Keep in mind that the height in the trapezoid is DB.

S=(4+8)2×3 S=\frac{(4+8)}{2}\times3

S=12×32=362=18 S=\frac{12\times3}{2}=\frac{36}{2}=18

Answer

18

Exercise #7

Given the rectangle ABCD

It is known that:

AB=4

AD=3

What is the length of the diagonal BD?

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Video Solution

Step-by-Step Solution

We will use the Pythagorean theorem in order to find BD:

BD2=AD2+AB2 BD^2=AD^2+AB^2

Let's input the known data:

BD2=32+42 BD^2=3^2+4^2

BD2=9+16 BD^2=9+16

BD2=25 BD^2=25

We'll take the square root:

BD=25=5 BD=\sqrt{25}=5

Answer

5 5

Exercise #8

Given that the triangle ABC is isosceles,
and inside it we draw EF parallel to CB:

171717888AAABBBCCCDDDEEEFFFGGG53 AF=5 AB=17
AG=3 AD=8
AD the height in the triangle

What is the area of the trapezoid EFBC?

Video Solution

Step-by-Step Solution

To find the area of the trapezoid, you must remember its formula:(base+base)2+altura \frac{(base+base)}{2}+\text{altura} We will focus on finding the bases.

To find GF we use the Pythagorean theorem: A2+B2=C2 A^2+B^2=C^2  In triangle AFG

We replace:

32+GF2=52 3^2+GF^2=5^2

We isolate GF and solve:

9+GF2=25 9+GF^2=25

GF2=259=16 GF^2=25-9=16

GF=4 GF=4

We will do the same process with side DB in triangle ABD:

82+DB2=172 8^2+DB^2=17^2

64+DB2=289 64+DB^2=289

DB2=28964=225 DB^2=289-64=225

DB=15 DB=15

From here there are two ways to finish the exercise:

  1. Calculate the area of the trapezoid GFBD, prove that it is equal to the trapezoid EGDC and add them up.

  2. Use the data we have revealed so far to find the parts of the trapezoid EFBC and solve.

Let's start by finding the height of GD:

GD=ADAG=83=5 GD=AD-AG=8-3=5

Now we reveal that EF and CB:

GF=GE=4 GF=GE=4

DB=DC=15 DB=DC=15

This is because in an isosceles triangle, the height divides the base into two equal parts then:

EF=GF×2=4×2=8 EF=GF\times2=4\times2=8

CB=DB×2=15×2=30 CB=DB\times2=15\times2=30

We replace the data in the trapezoid formula:

8+302×5=382×5=19×5=95 \frac{8+30}{2}\times5=\frac{38}{2}\times5=19\times5=95

Answer

95

Exercise #9

ABC is an isosceles triangle.

AD is the height of triangle ABC.555333171717888AAABBBCCCDDDEEEFFFGGG

AF = 5

AB = 17
AG = 3

AD = 8

What is the perimeter of the trapezoid EFBC?

Video Solution

Step-by-Step Solution

To find the perimeter of the trapezoid, all its sides must be added:

We will focus on finding the bases.

To find GF we use the Pythagorean theorem: A2+B2=C2 A^2+B^2=C^2 in the triangle AFG

We replace

32+GF2=52 3^2+GF^2=5^2

We isolate GF and solve:

9+GF2=25 9+GF^2=25

GF2=259=16 GF^2=25-9=16

GF=4 GF=4

We perform the same process with the side DB of the triangle ABD:

82+DB2=172 8^2+DB^2=17^2

64+DB2=289 64+DB^2=289

DB2=28964=225 DB^2=289-64=225

DB=15 DB=15

We start by finding FB:

FB=ABAF=175=12 FB=AB-AF=17-5=12

Now we reveal EF and CB:

GF=GE=4 GF=GE=4

DB=DC=15 DB=DC=15

This is because in an isosceles triangle, the height divides the base into two equal parts so:

EF=GF×2=4×2=8 EF=GF\times2=4\times2=8

CB=DB×2=15×2=30 CB=DB\times2=15\times2=30

All that's left is to calculate:

30+8+12×2=30+8+24=62 30+8+12\times2=30+8+24=62

Answer

62

Exercise #10

Shown below is the rectangle ABCD.

Given in cm:

AK = 5

DK = 4

The area of the rectangle is 24 cm².

Calculate the side AB.

S=24S=24S=24555444AAABBBCCCDDDKKK

Video Solution

Step-by-Step Solution

Let's look at triangle ADK in order to calculate side AD:

AD2+DK2=AK2 AD^2+DK^2=AK^2

Now let's substitute in our values:

AD2+42=52 AD^2+4^2=5^2

AD2+16=25 AD^2+16=25

We'll then move 16 to the other side and change the sign to the appropriate one:

AD2=2516 AD^2=25-16

AD2=9 AD^2=9

Next, we'll take the square root and get:

AD=3 AD=3

Since AD is a side of rectangle ABCD, we can calculate side AB as follows:

S=AB×AD S=AB\times AD

Let's substitute in our values:

24=3×AB 24=3\times AB

Finally, we'll divide both sides by 3:

AB=8 AB=8

Answer

8

Exercise #11

Look at the triangle and circle below.

Which has the larger perimeter/circumference?

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Video Solution

Step-by-Step Solution

To determine which has the larger measurement, the triangle's perimeter or the circle's circumference, we need to compute both values.

Step 1: Calculate the perimeter of the Triangle
We are given two sides of the triangle: 6 and 5. Since it's implied to be a right triangle, we apply the Pythagorean theorem to find the third side, the hypotenuse c c :

c=62+52=36+25=61 c = \sqrt{6^2 + 5^2} = \sqrt{36 + 25} = \sqrt{61}

The perimeter P P of the triangle is:

P=6+5+6111+7.81=18.81 P = 6 + 5 + \sqrt{61} \approx 11 + 7.81 = 18.81

Step 2: Calculate the circumference of the Circle
The circumference C C of a circle with radius r r is given by the formula:

C=2πr C = 2 \pi r

Assuming the radius of the circle is equivalent to the '6' mentioned for the green line in the SVG:

C=2π×637.7 C = 2 \pi \times 6 \approx 37.7

Step 3: Compare the Triangle's Perimeter and the Circle's Circumference
We compare the values:

  • Perimeter of the Triangle: P18.81 P \approx 18.81
  • Circumference of the Circle: C37.7 C \approx 37.7

The circumference of the circle (37.7) is greater than the perimeter of the triangle (18.81).

Therefore, the circle has the larger measurement.

Conclusion: The circle has the larger perimeter.

Answer

The circle

Exercise #12

ABCD is a kite.

BD is the diagonal of a square that has an area equal to 36 cm².

AC=2x AC=2x

Express the area of the kite in terms of X.

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Video Solution

Step-by-Step Solution

To solve this problem, we'll follow these steps:

  • Step 1: Calculate the side length of the square using the given area.
  • Step 2: Determine the length of BDBD using the side length.
  • Step 3: Use the kite area formula with diagonals BDBD and AC=2xAC=2x.

Now, let's work through each step:

Step 1: The area of the square is 36 cm². The side length of the square, denoted as ss, can be calculated by taking the square root of the area:

s=36=6 cms = \sqrt{36} = 6 \text{ cm}

Step 2: To find diagonal BDBD, we use the relationship for the diagonal of a square in terms of its side:

BD=s2BD = s \sqrt{2}. Given s=6s = 6, we compute:

BD=62 cmBD = 6\sqrt{2} \text{ cm}

Step 3: Now, we apply the formula for the area of a kite, which is 12×d1×d2\frac{1}{2} \times d1 \times d2, where d1=BD=62d1 = BD = 6\sqrt{2} and d2=AC=2xd2 = AC = 2x:

The area AA of the kite is:

A=12×62×2x=62x cm2A = \frac{1}{2} \times 6\sqrt{2} \times 2x = 6\sqrt{2}x \text{ cm}^2

Therefore, the area of the kite in terms of xx is 62x6\sqrt{2}x cm².

Answer

62x 6\sqrt{2}x cm²

Exercise #13

AAABBBCCCDDDEEEFFF16810

ΔADEΔFCE ΔADE∼Δ\text{FCE}

Calculate the perimeter of the given rectangle ABCD.

Video Solution

Step-by-Step Solution

Let's begin by observing triangle FCE and calculate side FC using the Pythagorean theorem:

EC2+FC2=EF2 EC^2+FC^2=EF^2

Let's begin by substituting all the known values into the formula:

82+FC2=102 8^2+FC^2=10^2

64+FC2=100 64+FC^2=100

FC2=10064 FC^2=100-64

FC2=36 FC^2=36

Let's take the square root:

FC=6 FC=6

Since we know that the triangles overlap:

ADFC=DECE=AEFE \frac{AD}{FC}=\frac{DE}{CE}=\frac{AE}{FE}

Let's again substitute the known values into the formula:

AD6=168 \frac{AD}{6}=\frac{16}{8}

AD=2×6=12 AD=2\times6=12

Finally let's calculate side CD:

16+8=24 16+8=24

Since in a rectangle each pair of opposite sides are equal, we can calculate the perimeter of rectangle ABCD as follows:

12+24+12+24=24+48=72 12+24+12+24=24+48=72

Answer

72

Exercise #14

Given a circle whose center O. From the center of the circle go out 2 radii that cut the circle at the points A and B.

Given AO⊥OB.

The side AB is equal to and+2.

Express band and the area of the circle.

y+2y+2y+2AAABBBOOO

Video Solution

Step-by-Step Solution

To solve this problem, we'll follow these steps:

  • Identify the given information.
  • Use the geometric properties of a circle and a right triangle to find the radius.
  • Express the area of the circle in terms of the given expression.

Now, let's work through each step:

Step 1: Given a circle with center O O and radii AO AO and OB OB such that AOOB AO\perp OB , each is a radius r r , and AB=and+2 AB = \text{and}+2 .

Step 2: By the Pythagorean theorem, we know:

AO2+OB2=AB2 AO^2 + OB^2 = AB^2 r2+r2=(y+2)2 r^2 + r^2 = (y+2)^2 2r2=y2+4y+4 2r^2 = y^2 + 4y + 4

Step 3: Solving for the area of the circle:

The radius r r can be expressed by rearranging:

r2=y2+4y+42 r^2 = \frac{y^2 + 4y + 4}{2}

The area of the circle using this radius is:

Area=πr2=π(y2+4y+42)=π2(y2+4y+4) \text{Area} = \pi r^2 = \pi \left(\frac{y^2 + 4y + 4}{2}\right) = \frac{\pi}{2}(y^2 + 4y + 4)

Therefore, the expression for the area of the circle is π2[y2+4y+4] \frac{\pi}{2}[y^2+4y+4] .

Answer

π2[y2+4y+4] \frac{\pi}{2}[y^2+4y+4]

Exercise #15

ABCD is a parallelogram
BFCE is a deltoid

555999444AAABBBCCCDDDFFFEEEHHHGGG7.5

What is the area of the parallelogram ABCD?

Video Solution

Step-by-Step Solution

First, we must remember the formula for the area of a parallelogram:Lado x Altura \text{Lado }x\text{ Altura} .

In this case, we will try to find the height CH and the side BC.

We start from the side

First, let's observe the small triangle EBG,

As it is a right triangle, we can use the Pythagorean theorem (

A2+B2=C2 A^2+B^2=C^2 )

BG2+42=52 BG^2+4^2=5^2

BG2+16=25 BG^2+16=25

BG2=9 BG^2=9

BG=3 BG=3

Now, let's start looking for GC.

First, remember that the deltoid has two pairs of equal adjacent sides, therefore:FC=EC=9 FC=EC=9

Now we can also do Pythagoras in the triangle GCE.

GC2+42=92 GC^2+4^2=9^2

GC2+16=81 GC^2+16=81

GC2=65 GC^2=65

GC=65 GC=\sqrt{65}

Now we can calculate the side BC:

BC=BG+GT=3+6511 BC=BG+GT=3+\sqrt{65}\approx11

Now, let's observe the triangle BGE and DHC

Angle BGE = 90°
Angle CHD = 90°
Angle CDH=EBG because these are opposite parallel angles.

Therefore, there is a ratio of similarity between the two triangles, so:

HDBG=HCGE \frac{HD}{BG}=\frac{HC}{GE}

HDBG=7.53=2.5 \frac{HD}{BG}=\frac{7.5}{3}=2.5

HCEG=HC4=2.5 \frac{HC}{EG}=\frac{HC}{4}=2.5

HC=10 HC=10

Now that there is a height and a side, all that remains is to calculate.

10×11110 10\times11\approx110

Answer

110 \approx110

Exercise #16

777

Is the sum of the two diagonals in the above square greater than the sum of the 3 sides of the square?

Video Solution

Answer

No

Exercise #17

Look at the square below:

111111

Is the sum of the two diagonals greater than the sum of the 3 sides of the square?

Video Solution

Answer

False

Exercise #18

Look at the square below:

333

Is the sum of the two diagonals greater than the sum of the 3 sides of the square?

Video Solution

Answer

No

Exercise #19

Look at the square below:

666

Is the sum of the two diagonals greater than the sum of the 3 sides of the square?

Video Solution

Answer

No

Exercise #20

ABCD is a square with a side length of 8 cm.

EB = 10

What is the area of the parallelogram EBFC?

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Video Solution

Answer

112 cm²