Equivalent Expressions

1. Oct 27, 2016

Veronica_Oles

1. The problem statement, all variables and given/known data
State an equivalent expression in terms of the related acute angle?
(A) cot(-π/4)

2. Relevant equations

3. The attempt at a solution
(A) I made the the unit circle and since its negative I went clockwise and made it into the fourth quadrant. I ended up getting -cotπ/4. However the answer is not the one that the text book has given. Im a little confused.
The text book has given the answer cot3π/4, but I thought we were supposed to go clockwise because it is negative?

2. Oct 27, 2016

PeroK

An acute angle is one that is less than $\pi /2$. I've never seen this used for negative angles, so I'm not sure whether $-\pi /4$ would be considered acute. In any case, $3\pi /4$ is not an acute angle. It's actually a "reflex" angle (I had to look that one up).

I thought your answer was correct. $\pi /4$ is definitely an acute angle.

Last edited: Oct 27, 2016
3. Oct 27, 2016

Staff: Mentor

I agree with @PeroK -- $3\pi/4$ is not an acute angle.
I'll bet what you actually looked up was "reflex".

4. Oct 27, 2016

Veronica_Oles

I just asked my teacher, I got the angle correct. Thx.