Examples with solutions for Using the Pythagorean Theorem: Calculation using the diagonal

Exercise #1

Look at the following rectangle:

AAABBBCCCDDD106

Calculate the perimeter of the rectangle ABCD.

Video Solution

Step-by-Step Solution

Let's focus on triangle BCD in order to find side DC

We'll use the Pythagorean theorem and input the known data:

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

62+DC2=102 6^2+DC^2=10^2

DC2=10036=64 DC^2=100-36=64

Let's take the square root:

DC=8 DC=8

Since in a rectangle each pair of opposite sides are equal to each other, we can state that:

DC=AB=8 DC=AB=8

BC=AD=6 BC=AD=6

Now we can calculate the perimeter of the rectangle by adding all sides together:

8+6+8+6=16+12=28 8+6+8+6=16+12=28

Answer

28

Exercise #2

AAABBBCCCDDD2524Calculate the perimeter of the rectangle ABCD.

Video Solution

Step-by-Step Solution

Let's focus on triangle BCD in order to find side BC

We'll use the Pythagorean theorem and input the known data:

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

BC2+242=252 BC^2+24^2=25^2

BC2=625576=49 BC^2=625-576=49

Let's take the square root:

BC=7 BC=7

Since in a rectangle, each pair of opposite sides are equal to each other, we can state that:

DC=AB=24 DC=AB=24

BC=AD=7 BC=AD=7

Now we can calculate the perimeter of the rectangle by adding all sides together:

24+7+24+7=14+48=62 24+7+24+7=14+48=62

Answer

62

Exercise #3

Look at the following rectangle:

AAABBBCCCDDD178

BC = 8

BD = 17

Calculate the area of the rectangle ABCD.

Video Solution

Step-by-Step Solution

We will find side DC by using the Pythagorean theorem in triangle DBC:

BC2+CD2=BD2 BC^2+CD^2=BD^2

Let's substitute the known data:

82+CD2=172 8^2+CD^2=17^2

CD2=28964=225 CD^2=289-64=225

Let's take the square root:

CD=15 CD=15

Now we have the length and width of rectangle ABCD and we'll calculate the area:

15×8=120 15\times8=120

Answer

120

Exercise #4

ABCD is a rectangle.

AC = 13

AB = 12

Calculate the length of the side BC.

Video Solution

Step-by-Step Solution

When writing the name of a polygon, the letters will always be in the order of the sides:

This is a rectangle ABCD:

This is a rectangle ABDC:

Always go in order, and always with the right corner to the one we just mentioned.

Answer

5

Exercise #5

Below is the rectangle ABCD.

O is the intersection point of the diagonals of the rectangle.

AD = 8

BO = 8.5

Calculate the area of the triangle ABD.

AAABBBCCCDDDOOO8.58

Video Solution

Step-by-Step Solution

According to the given information, we can claim that:

BD=2BO=8.5×2=17 BD=2BO=8.5\times2=17

Now let's look at triangle ABD to calculate side AB

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

Let's input the known data:

AB2+82=172 AB^2+8^2=17^2

AB2=28964=225 AB^2=289-64=225

We'll take the square root

AB=15 AB=15

Now let's calculate the area of triangle ABD:

15×82=1202=60 \frac{15\times8}{2}=\frac{120}{2}=60

Answer

60

Exercise #6

Look at the following rectangle:

AAABBBCCCDDD54

DC = 4

AC = 5

Calculate the area of the rectangle ABCD.

Video Solution

Answer

12

Exercise #7

Look at the following rectangle:

AAABBBCCCDDD1213

Calculate the area of the triangle ABC.

Video Solution

Answer

30

Exercise #8

Look at the following rectangle:

AAABBBCCCDDD158

Calculate the perimeter of the triangle ABD.

Video Solution

Answer

40

Exercise #9

Given the rectangle such that:

O is the intersection point of the diagonals of the rectangle.

Given: AD=6 , AB=8

Calculate the length of the section BO.

AAABBBCCCDDDOOO86

Video Solution

Answer

5

Exercise #10

Below is the rectangle ABCD.

O is the intersection point of the diagonals of the rectangle.

DC = 15

OC = 8.5

Calculate the area of the rectangle ABCD.

AAABBBCCCDDDOOO8.515

Video Solution

Answer

120