# Thread: sine and cosine functions

1. ## sine and cosine functions

Given that Q is approximately (0.259,0.966) is a point on the unit circle with angle 75 degrees, estimate sin 285 degrees and cos 285 degrees without a calculator.

I am stuck!

2. Originally Posted by Kate182
Given that Q is approximately (0.259,0.966) is a point on the unit circle with angle 75 degrees, estimate sin 285 degrees and cos 285 degrees without a calculator.

I am stuck!
Ok use a reference angle for 285. So the reference angle would be 75.

Now use sum identity formula

$\cos{(45 +30)}=\cos{45}\cos{30}-\sin{45}\sin{30}$