What is the general solution of cos¹⁰⁰ x - sin¹⁰⁰ x = 1?

In a triangle ABC tan A + tan B + tan C = k  What is the value of cot A cot B cot C? 

What is sin12° sin48° equal to? 

What is $\rm \frac{\cos 17^\circ-\sin 17^\circ}{\cos 17^\circ+\sin ^\circ}$ equal to