# Thread: Really basic trig question

1. ## Really basic trig question

OK:
arsin(sin(5p\7)) = 2p/7
arctan(tan(5p/5))= -p/5

Why is the second answer negative?

2. ## Re: Really basic trig question Originally Posted by Nervous OK:
arsin(sin(5p\7)) = 2p/7
arctan(tan(5p/5))= -p/5

Why is the second answer negative?
The angle must be in the second quadrant...

3. ## Re: Really basic trig question Originally Posted by Nervous OK:
arsin(sin(5p\7)) = 2p/7
arctan(tan(5p/5))= -p/5

Why is the second answer negative?
uhhh ... arctan((tan(5pi/5)) = \arctan(tan(pi)) = \arctan(0) = 0

4. ## Re: Really basic trig question Originally Posted by skeeter uhhh ... arctan((tan(5pi/5)) = \arctan(tan(pi)) = \arctan(0) = 0
I must have misunderstood the question, I thought that p was representing some unknown, not \displaystyle \displaystyle \begin{align*} \pi \end{align*}...

5. ## Re: Really basic trig question Originally Posted by Prove It I must have misunderstood the question, I thought that p was representing some unknown, not \displaystyle \displaystyle \begin{align*} \pi \end{align*}...
first solution is ...
arsin(sin(5p\7)) = 2p/7
what else could "p" be?

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