Cosine Exact Values
Radians to Degrees
By looking at the unit circle, we can see 315 degrees is located in bottom right corner where cosine is positive. Using our Sine, Cosine, Tangent table, we know the cosine of 45 degrees, is sqrt. 2/ 2
Now that we have the degree equivalent to 7pi/4 radians we need to once again use a unit circle to figure out the equivalent 45-45-90 degree triangle measurements.
Cos (315 degrees)
Finding the degree value for a cosine functions the same way as for a sine. You must find the degree for the specific radian by setting up a proportion. You must then use a unit circle or 30-60-90/ 45-45-90 triangle tables in order to find the radian mode (do NOT forget the negatives)