Examples with solutions for Using the Pythagorean Theorem: Applying the formula

Exercise #1

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What is the length of the hypotenuse?

Video Solution

Step-by-Step Solution

We use the Pythagorean theorem

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

We insert the known data:

32+42=BC2 3^2+4^2=BC^2

9+16=BC2 9+16=BC^2

25=BC2 25=BC^2

We extract the root:

25=BC \sqrt{25}=BC

5=BC 5=BC

Answer

5

Exercise #2

Look at the triangle in the diagram. How long is side AB?

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Video Solution

Step-by-Step Solution

To find side AB, we will need to use the Pythagorean theorem.

The Pythagorean theorem allows us to find the third side of a right triangle, if we have the other two sides.

You can read all about the theorem here.

Pythagorean theorem:

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

That is, one side squared plus the second side squared equals the third side squared.

We replace the existing data:

32+22=AB2 3^2+2^2=AB^2

9+4=AB2 9+4=AB^2

13=AB2 13=AB^2

We find the root:

13=AB \sqrt{13}=AB

Answer

13 \sqrt{13} cm

Exercise #3

Look at the triangle in the diagram. Calculate the length of side AC.

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Video Solution

Step-by-Step Solution

To solve the exercise, we have to use the Pythagorean theorem:

A²+B²=C²

 

We replace the data we have:

3²+4²=C²

9+16=C²

25=C²

5=C

Answer

5 cm

Exercise #4

Consider a right-angled triangle, AB = 8 cm and AC = 6 cm.
Calculate the length of side BC.

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Step-by-Step Solution

To find the length of the hypotenuse BC in a right-angled triangle where AB and AC are the other two sides, we use the Pythagorean theorem: c2=a2+b2 c^2 = a^2 + b^2 .

Here, a=6 cm a = 6 \text{ cm} and b=8 cm b = 8 \text{ cm} .

Plugging the values into the Pythagorean theorem, we get:

c2=62+82 c^2 = 6^2 + 8^2 .

Calculating further:

c2=36+64 c^2 = 36 + 64

c2=100 c^2 = 100 .

Taking the square root of both sides gives:

c=10 cm c = 10 \text{ cm} .

Answer

10 cm

Exercise #5

Look at the triangle in the diagram. How long is side BC?

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Video Solution

Step-by-Step Solution

To solve the exercise, it is necessary to know the Pythagorean Theorem:

A²+B²=C²

We replace the known data:

2²+B²=7²

4+B²=49

We input into the formula:

B²=49-4

B²=45

We find the root

B=√45

This is the solution. However, we can simplify the root a bit more.

First, let's break it down into prime numbers:

B=√(9*5)

We use the property of roots in multiplication:

B=√9*√5

B=3√5

This is the solution!

Answer

35 3\sqrt{5} cm

Exercise #6

Given the triangle ABC, find the length BC

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Video Solution

Step-by-Step Solution

To answer this question, we must know the Pythagorean Theorem

The theorem allows us to calculate the sides of a right triangle.

We identify the sides:

ab = a = 5
bc = b = ?

ac = c = 13

 

We replace the data in the exercise:

5²+?² = 13²

We swap the sections

?²=13²-5²

?²=169-25

?²=144

?=12

Answer

12 cm