Question

(1)化简sin(α-)+cos(α+);

(2)化简sin(15°+α)-cos(75°-α).

Answer 1

解:（1）原式=sin(α-)+cos［+(α-)］

=sin(α-)-sin(α-)

=0.

（2）原式=sin［90°-(75°-α)］-cos(75°-α)

=cos(75°-α)-cos(75°-α)

=0.