30, 60, 90 triangle
1, sqrt 3, 2
sin 30 = 1/2
cos 30 = sqrt 3/2
cos is negative in quad 2 and quad 3
so
180 - 30 = 150 degrees
180 + 30 = 210 degrees
How do I do this? Without a calculator, determine two angles between 0 degrees and 360 degrees that have a cosine of negative square root 3 over 2.
1 answer