Question
Evaluate in simple surd form the following:
(1) Sin 225
(2) Cos 195
(3) Sin 345
(4) tan 195
(1) Sin 225
(2) Cos 195
(3) Sin 345
(4) tan 195
Answers
oobleck
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)
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)