Question

trig equation tan ()=-1

Answer 1

This will most likely be in the front or back cover of your textbook.

Answer 2

If you haven't memorized it:
arctan(1) = pi/4

Answer 3

And since the negative goes right through for tan(#), and sin(#) too
attach a negative to that pi/4

Answer 4

Funny, you posted. I was doing calculus homework and needed the arctan of this for the bounds of an integral.

Answer 5

Tan=sin/cos
pi/4=45degree
(rad2/2/rad2/2)=1
-1 cause arch