Question

Find cos(405°) and sin(405°). Identify the measure of the reference angle.

Answer 1

Reference angle will be
`45^(\circ)`

`cos(45^(\circ))=0.707`

`sin(45^(\circ))=0.707`

Explanation:

We have given
`cos(405^(\circ))`

Which can be written as
`cos(405^(\circ))=cos(360+45)`

We know that
`45^(\circ)` is present in first quadrant

And in first quadrant the reference angle is angle itself

So reference angle will be = 45°

Now
`cos(405)=cos(2\pi +45)=cos45^(\circ)=0.707`

And
`sin(405)=sin(2\pi +45)=sin45^(\circ)=0.707`