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The Baudhayana-Pythagoras Theorem - Hypotenuse of an Isosceles Right Triangle

Grade 8CBSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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The Baudhayana-Pythagoras theorem states that in a right-angled triangle, the square of the hypotenuse is equal to the sum of the squares of the other two sides: h2=a2+b2h^2 = a^2 + b^2.

A right-angled triangle with sides labeled a, b and hypotenuse h.
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An Isosceles Right Triangle is a special case where the two legs (base and perpendicular) are equal in length (a=ba = b).

An isosceles right triangle with equal sides marked with tick marks.
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In an isosceles right triangle, the relationship between the hypotenuse hh and equal sides aa simplifies to h2=2a2h^2 = 2a^2, which implies h=a2h = a\sqrt{2}.

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The value of 2\sqrt{2} is approximately 1.4141.414, which can be used for numerical estimations of the hypotenuse length.

📐Formulae

h2=a2+b2h^2 = a^2 + b^2

In an isosceles right triangle: h2=a2+a2=2a2\text{In an isosceles right triangle: } h^2 = a^2 + a^2 = 2a^2

h=a2h = a\sqrt{2}

a=h2a = \frac{h}{\sqrt{2}}

💡Examples

Problem 1:

Find the length of the hypotenuse of an isosceles right triangle whose equal sides are each 6 cm6\text{ cm} long.

Solution:

Let the equal sides be a=6 cma = 6\text{ cm}. According to the Baudhayana-Pythagoras theorem: h2=a2+a2h^2 = a^2 + a^2 h2=62+62h^2 = 6^2 + 6^2 h2=36+36h^2 = 36 + 36 h2=72h^2 = 72 h=72=36×2h = \sqrt{72} = \sqrt{36 \times 2} h=62 cmh = 6\sqrt{2}\text{ cm}

Explanation:

Since the triangle is an isosceles right triangle, we substitute the side length into the derived formula h=a2h = a\sqrt{2}.

Problem 2:

If the hypotenuse of an isosceles right triangle is 10 cm10\text{ cm}, find the length of its equal sides.

Solution:

Let the equal sides be aa. The hypotenuse h=10 cmh = 10\text{ cm}. Using the formula h2=2a2h^2 = 2a^2: 102=2a210^2 = 2a^2 100=2a2100 = 2a^2 Dividing by 22: a2=50a^2 = 50 a=50=25×2a = \sqrt{50} = \sqrt{25 \times 2} a=52 cma = 5\sqrt{2}\text{ cm}

Explanation:

We use the relationship for isosceles right triangles where the square of the hypotenuse is twice the square of one side, then solve for the side length.

Problem 3:

Verify the Baudhayana theorem for a triangle with sides 3 cm3\text{ cm}, 3 cm3\text{ cm}, and hypotenuse 18 cm\sqrt{18}\text{ cm}.

Solution:

The two equal sides are a=3a = 3 and b=3b = 3. The hypotenuse is c=18c = \sqrt{18}. Calculate a2+b2a^2 + b^2: 32+32=9+9=183^2 + 3^2 = 9 + 9 = 18 Calculate c2c^2: (18)2=18(\sqrt{18})^2 = 18 Since a2+b2=c2a^2 + b^2 = c^2, the theorem is verified.

Explanation:

By squaring the legs and the hypotenuse, we show that the sum of the squares of the legs equals the square of the hypotenuse.

Problem 4:

Calculate the hypotenuse of an isosceles right triangle if each of the equal sides measures 5 cm5\text{ cm}.

Isosceles right triangle with sides of 5 cm.

Solution:

Given side a=5 cma = 5\text{ cm}. Using the formula for isosceles right triangles: h=a2h = a\sqrt{2} h=52 cmh = 5\sqrt{2}\text{ cm} Alternatively: h2=52+52h^2 = 5^2 + 5^2 h2=25+25=50h^2 = 25 + 25 = 50 h=50=52 cmh = \sqrt{50} = 5\sqrt{2}\text{ cm} Using 2≈1.414\sqrt{2} \approx 1.414: h≈5×1.414=7.07 cmh \approx 5 \times 1.414 = 7.07\text{ cm}

Explanation:

Since both sides are equal, we apply the Pythagoras theorem where both the base and perpendicular are 5 cm.

Problem 5:

The hypotenuse of an isosceles right triangle is 32 cm\sqrt{32}\text{ cm}. Find the length of the equal sides.

Isosceles right triangle with hypotenuse square root of 32.

Solution:

Let the length of each equal side be aa. Given h=32 cmh = \sqrt{32}\text{ cm}. Using the formula h2=2a2h^2 = 2a^2: (32)2=2a2(\sqrt{32})^2 = 2a^2 32=2a232 = 2a^2 a2=322=16a^2 = \frac{32}{2} = 16 a=16=4 cma = \sqrt{16} = 4\text{ cm} Thus, the equal sides are 4 cm4\text{ cm} each.

Explanation:

We use the relationship between the hypotenuse and the sides of an isosceles right triangle to solve for the side length.

Hypotenuse of an Isosceles Right Triangle Class 8 Notes & Examples