Question

How do you find the exact values `cos (pi/4)` using the special triangles?

Answer 1

`cos(pi/4) = 1/sqrt(2)`

Explanation:

The "special triangle" corresponding to `pi/4` is an isosceles triangle with equal adjacent and opposite sides (and a hypotenuse that can be calculated using the Pythagorean Theorem).

By definition
`color(white)("XXXX")` `cos = ("adjacent")/("hypontenuse")`