By using the 30-60-90 right triangle, or the unit circle, you can find (without a calculator) that
[tex]\cos30^o=\sqrt{3} /2[/tex]
[tex]\cos60^o=1/2[/tex]
[tex]\cos90^o=0[/tex]
Thus, cos(30°) + cos(60°) > cos(90°) and they are not equal to each other.
