Question

If two angles of an isosceles triangle measure 35° and the base of the triangle is 18 feet, find the perimeter of the triangle.

Answer 1

40

Explanation:

You can split it down the middle to form 2 right triangles. Then, use the rules of sin, cosin, and tan to figure out the length of the sides.

You have the bottom side is 9 (because you split the original triangle in half, so 18/2 = 9) and that the angle next to that side is 35. You are trying to find the hypotenuse because that will help you find the perimeter.

You can use cosin(angle) = adjacent/hypotenuse

you have:

angle = 35

adjacent = 9

hypotenuse = unknown, call it x

So you can plug those values into your equation and you would have:

cosin(35) = 9/x

Rearranging the terms, you have:

x = 9/cosin(35)

Put this in a calculator and you will get x = about 11

To find the perimeter, just do 11 + 11 + 18 = 40 feet