Examples with solutions for Using the Pythagorean Theorem: Calculate The Missing Side based on the formula

Exercise #1

888XXX171717

What is the length of the side marked X?

Video Solution

Step-by-Step Solution

We use the Pythagorean theorem:

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

Answer

15 15

Exercise #2

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

222777AAABBBCCC

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 #3

Given the triangle ABC, find the length BC

131313555AAACCCBBB

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

Exercise #4

Triangle ABC is a right triangle,

Find BC

35ABC

Step-by-Step Solution

To solve this problem, we'll perform the following steps:

  • Step 1: Identify the sides of the triangle. The problem states AB=5 AB = 5 and AC=3 AC = 3 . Since triangle ABC is a right triangle, AB=5 AB = 5 is the hypotenuse.

  • Step 2: Apply the Pythagorean Theorem, which states a2+b2=c2 a^2 + b^2 = c^2 , where c c is the hypotenuse.

  • Step 3: In this case, set CA=3 CA = 3 , BC=x BC = x , and AB=5 AB = 5 . Substitute these into the theorem:
    32+x2=52 3^2 + x^2 = 5^2

  • Step 4: Calculate 32=9 3^2 = 9 and 52=25 5^2 = 25 . Thus, the equation becomes:
    9+x2=25 9 + x^2 = 25

  • Step 5: Rearrange to solve for x2 x^2 :
    x2=259 x^2 = 25 - 9
    x2=16 x^2 = 16

  • Step 6: Solve for x x by taking the square root:
    x=16=4 x = \sqrt{16} = 4

Therefore, the length of side BC is 4 4 .

Answer

4 4

Exercise #5

Triangle ABC is a right triangle,

Find X X

5X7ABC

Step-by-Step Solution

To solve the given problem, we will use the Pythagorean Theorem, which is stated as:

a2+b2=c2 a^2 + b^2 = c^2

Here, c c represents the hypotenuse, and a a and b b are the legs of the right triangle. Based on our problem:

  • c=7 c = 7 (the hypotenuse)
  • a=5 a = 5 (one of the legs)
  • b=X b = X (the missing side we need to find)

Applying the Pythagorean theorem, we get:

52+X2=72 5^2 + X^2 = 7^2

Calculating the squares, we have:

25+X2=49 25 + X^2 = 49

Subtracting 25 from both sides to isolate X2 X^2 :

X2=4925 X^2 = 49 - 25

X2=24 X^2 = 24

Taking the square root of both sides to solve for X X :

X=24 X = \sqrt{24}

Therefore, the solution to the problem is X=24 X = \sqrt{24} , which corresponds to choice 1 in the multiple-choice answers.

Answer

24 \sqrt{24}

Exercise #6

Triangle ABC is a right triangle,

Find AB

69ABC

Step-by-Step Solution

To find the length of side AB AB in the right triangle ABC \triangle ABC , we will use the Pythagorean Theorem. The theorem is given by:

a2+b2=c2 a^2 + b^2 = c^2

In this equation, c c is the hypotenuse, and a a and b b are the other two sides. Based on the given information, we have:

  • AC=6 AC = 6 is one leg.
  • BC=9 BC = 9 is the hypotenuse.
  • AB AB is the unknown leg we want to find.

Substituting the known values into the Pythagorean Theorem:

AB2+62=92 AB^2 + 6^2 = 9^2

Simplifying the equation:

AB2+36=81 AB^2 + 36 = 81

Subtract 36 from both sides to solve for AB2 AB^2 :

AB2=8136 AB^2 = 81 - 36

AB2=45 AB^2 = 45

To find AB AB , take the square root of both sides:

AB=45 AB = \sqrt{45}

Therefore, the length of side AB AB is 45 \sqrt{45} .

Answer

45 \sqrt{45}

Exercise #7

Triangle ABC is a right triangle,

Find AB

6ABC

Step-by-Step Solution

To find the length of side AB in the right triangle ABC:

  • Step 1: Identify the known lengths. We know BC=6BC = 6 and AC=72AC = \sqrt{72}.
  • Step 2: Apply the Pythagorean Theorem: AB2+BC2=AC2AB^2 + BC^2 = AC^2.
  • Step 3: Plug in the known values: AB2+62=(72)2AB^2 + 6^2 = (\sqrt{72})^2.
  • Step 4: Since (72)2=72(\sqrt{72})^2 = 72, the equation becomes AB2+36=72AB^2 + 36 = 72.
  • Step 5: Subtract 36 from both sides, yielding: AB2=36AB^2 = 36.
  • Step 6: Take the square root of each side: AB=36=6AB = \sqrt{36} = 6.

Thus, the length of side AB is 6 6 .

Answer

6 6

Exercise #8

Triangle ABC is a right triangle,

Find AB

510ABC

Step-by-Step Solution

To find the length of side AB AB in the right triangle ABC ABC , we will use the Pythagorean theorem:

Since BC BC is the hypotenuse, BC=10 BC = 10 , and one leg AC=5 AC = 5 , we can express the Pythagorean theorem as:

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

Substituting the known values gives us:

AB2+52=102 AB^2 + 5^2 = 10^2

Simplifying further:

AB2+25=100 AB^2 + 25 = 100

Subtracting 25 from both sides results in:

AB2=75 AB^2 = 75

Taking the square root of both sides, we obtain:

AB=75 AB = \sqrt{75}

Therefore, the length of side AB AB is 75 \sqrt{75} .

Answer

75 \sqrt{75}

Exercise #9

Triangle ABC is a right triangle,

Find AB

12ABC

Step-by-Step Solution

To solve the problem, we will use the Pythagorean Theorem to calculate the length of side AB AB . According to the theorem, AB2+AC2=BC2 AB^2 + AC^2 = BC^2 .

Given:

  • Hypotenuse BC=2 BC = 2
  • One leg AC=1 AC = 1

We need to find AB AB : AB2+12=22 AB^2 + 1^2 = 2^2

Solve for AB2 AB^2 : AB2+1=4 AB^2 + 1 = 4

By subtracting 1 from both sides: AB2=41=3 AB^2 = 4 - 1 = 3

Taking the square root of both sides gives us: AB=3 AB = \sqrt{3}

Therefore, the length of side AB AB is 3 \sqrt{3} .

Answer

3 \sqrt{3}

Exercise #10

Triangle ABC is a right triangle,

Find BC

620ABC

Step-by-Step Solution

To solve for BC BC in the right triangle ABC \triangle ABC , we follow these steps:

  • Identify the given lengths: AB=6 AB = 6 and AC=20 AC = 20 .
  • Apply the Pythagorean Theorem: AB2+BC2=AC2 AB^2 + BC^2 = AC^2 .
  • Substitute known values into the formula:

62+BC2=202 6^2 + BC^2 = 20^2

Simplify the left side:

36+BC2=400 36 + BC^2 = 400

Subtract 36 from both sides:

BC2=40036 BC^2 = 400 - 36

BC2=364 BC^2 = 364

Solve for BC BC by taking the square root of both sides:

BC=364 BC = \sqrt{364}

Thus, the length of BC BC is 364\sqrt{364}.

Answer

364 \sqrt{364}

Exercise #11

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 using our values:

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 now remove the square root:

BC=7 BC=7

Since each pair of opposite sides are equal to each other in a rectangle, 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 #12

Look at the following rectangle:

AAABBBCCCDDD1312

AB = 12

AC = 13

Calculate the area of the triangle BCD.

Video Solution

Step-by-Step Solution

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

  • Step 1: Use the Pythagorean Theorem to calculate the length of AD AD .
  • Step 2: Calculate the area of triangle BCD \triangle BCD .

Step 1: Given AB=12 AB = 12 and AC=13 AC = 13 , we use the Pythagorean Theorem to find AD AD .

AC2=AB2+AD2    132=122+AD2 AC^2 = AB^2 + AD^2 \implies 13^2 = 12^2 + AD^2 169=144+AD2    AD2=25    AD=5 169 = 144 + AD^2 \implies AD^2 = 25 \implies AD = 5

Step 2: Knowing the sides AD=5 AD = 5 (height of the rectangle) and AB=12 AB = 12 (base of the rectangle), triangle BCD \triangle BCD will have the base BC=12 BC = 12 and the height BD=5 BD = 5 .

The area of triangle BCD \triangle BCD is:

AreaBCD=12×base×height=12×12×5=30 \text{Area}_{\triangle BCD} = \frac{1}{2} \times \text{base} \times \text{height} = \frac{1}{2} \times 12 \times 5 = 30

Therefore, the area of triangle BCD \triangle BCD is 30.

Answer

30

Exercise #13

Look at the triangle in the figure.

What is the length of the hypotenuse given that its perimeter is 12+45 12+4\sqrt{5} cm?

444AAABBBCCC

Video Solution

Step-by-Step Solution

We calculate the perimeter of the triangle:

12+45=4+AC+BC 12+4\sqrt{5}=4+AC+BC

As we want to find the hypotenuse (BC), we isolate it:

12+454AC=BC 12+4\sqrt{5}-4-AC=BC

BC=8+45AC BC=8+4\sqrt{5}-AC

Then calculate AC using the Pythagorean theorem:

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

42+AC2=(8+45AC)2 4^2+AC^2=(8+4\sqrt{5}-AC)^2

16+AC2=(8+45)22×AC(8+45)+AC2 16+AC^2=(8+4\sqrt{5})^2-2\times AC(8+4\sqrt{5})+AC^2

We then simplify the two:AC2 AC^2

16=82+2×8×45+(45)22×8×AC2AC45 16=8^2+2\times8\times4\sqrt{5}+(4\sqrt{5})^2-2\times8\times AC-2AC4\sqrt{5}

16=64+645+16×516AC85AC 16=64+64\sqrt{5}+16\times5-16AC-8\sqrt{5}AC

16AC+85AC=64+645+16×516 16AC+8\sqrt{5}AC=64+64\sqrt{5}+16\times5-16

AC(16+85)=128+645 AC(16+8\sqrt{5})=128+64\sqrt{5}

AC=128+64516+85=8(16+85)16+85 AC=\frac{128+64\sqrt{5}}{16+8\sqrt{5}}=\frac{8(16+8\sqrt{5})}{16+8\sqrt{5}}

We simplify to obtain:

AC=8 AC=8

Now we can replace AC with the value we found for BC:

BC=8+45AC BC=8+4\sqrt{5}-AC

BC=8+458=45 BC=8+4\sqrt{5}-8=4\sqrt{5}

Answer

45 4\sqrt{5} cm