Question

Question #19655

Answer 1

If any angle, `A`, is drawn in standard position using a unit length hypotenuse triangle,
the angle `(-A)` has the same `x` coordinate and the same hypotenuse length and
`rarr cos(A) = cos(-A)`

Explanation:

For a triangle with unit length hypotenuse in standard position,
the `cos` of the angle at the origin is the `x` coordinate.

Since the `x` coordinate of `/_ A` is the same as the `x` coordinate of `/_-A`
`cos(A) = cos(-A)`