Question

An isosceles right triangle has legs of equal length if the hypotenuse is 10 cm long find the length of each leg

Answer 1

Since this is a right triangle, we know we have to use the Pythagorean Theorem: A² + B² = C² , where A and B = the legs of the triangle (which are shorter than the hypotenuse) and C = the hypotenuse.

In this isosceles triangle, A = B (because the legs are the same size) and C is 10cm longer than A and B.

Thus we get the following,

A = x

B = x

C = x + 10

We simply plug in these variables into the equation and solve for x:

x² + x² = (x+10)²

2x² = x² + 20x + 100

x² - 20x - 100 = 0

We solve for x by completing the square:

(x² - 20x + 100) - 100 = 100

(x-10)² -100 = 100

(x-10)² = 200

x - 10 = √(200)

x - 10 = 10 √2

x = 10 + 10√2 = 24

Finally,

A ≈ 24 (or 10 + 10√2)

B ≈ 24 (or 10 + 10√2)

C ≈ 24 + 10 ≈ 34 (or 10 + 10√2 + 10 = 20 + 10√2)