`cos(3pi)` Evalute the trigonometric function using its period as an aid

kspcr111 | Student

`cos(3pi)`

the periodicity of `cos (x)` is `cos(x+2pi)`

so,

`cos(3pi)` = `cos(pi+2Pi)`

           = `cos(pi) = -1`

so,

`cos(3pi) = -1`