Question

Find cos(−30°) and sin(−30°). Identify the measure of the reference angle.

Answer 1

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

`cos(-30)=0.866`

`sin(-30)=-0.5`

Explanation:

We have given angle =
`-30^(\circ)` which is equivalent to
`300^(\circ)`

We know that 300° lies in forth quadrant

For forth quadrant reference angle is given by
`300^(\circ)-angle`

So reference angle
`=360^(\circ)-300^(\circ)=30^(\circ)`

Now
`cos(-30)=cos(30)=0.866`

And
`sin(-30)=-sin(30)=-0.5`