Geometry. find the indicated side of the triangle. include a clear answer and description if possible

In this problem we are given a right triangle with 45 degree angle. We know that the sum of a triangle's angles needs to be equal to 180 degrees.

When we subtract 90+45 from 180 we got 45. That means we have an isoceles triangle.

According to the Pythagorean Theorem, .

When we plug in the numbers we get:

Because we know that a = b, we can write this as: or

Simplify: , then

Take the square root:

So, B is

To find it faster we have a formula for this: "If a right triangle has 2 equal angles, the hypotenuse is equal to times the leg."

Vice-versa: leg × = hypotenuse or leg = hypotenuse /

the surface area is 124cm²

step-by-step explanation:

length: 4cm

width: 9cm

height:   2cm