Evaluate in simple surd form the following:

Question

(1) Sin 225
(2) Cos 195
(3) Sin 345
(4) tan 195

Answer 1

remember your standard angles and half-angle formulas, then
sin225 = sin(180+45) = -sin45
cos195 = cos(180+15) = -cos15 = -cos(30/2)
sin345 = sin(360-15) = -sin15
tan195 = tan(180+15) = tan15 = tan(30/2)