arccos[sin(5pi/4)]
Evaluate w/o using a calculator. No decimal answers and use pi radians is necessary.

Question

arccos[sin(5pi/4)]
Evaluate w/o using a calculator. No decimal answers and use pi radians is necessary.

turingtest · Answer

what is sin 5pi/4 ?

anonymous · Answer

idk

anonymous · Answer

It is
$$
\sin( \pi +\frac \pi 4)
$$

anonymous · Answer

i still don't understand how to solve it

anonymous · Answer

find $\frac{5\pi}{4}$on the unit circle on the last page of the attached cheat sheet
the first coordinate is cosine, the second coordinate is sine
once you find $\sin(\frac{5\pi}{4})$ find the angle between 0 and $\pi$ whose cosine has the same value

turingtest · Answer

haha I have the same link with the same label^

anonymous · Answer

would the answer be 3pi/4

anonymous · Answer

you should find the point to have coordinates $(-\frac{\sqrt{2}}{2},-\frac{\sqrt{2}}{2})$
so $\cos(\frac{5\pi}{4})=-\frac{\sqrt{2}}{2}$ and $\sin(\frac{5\pi}{4})=-\frac{\sqrt{2}}{2}$

anonymous · Answer

yes, it would be $\frac{3\pi}{4}$

anonymous · Answer

You're a really good helper ! thank you.

anonymous · Answer

@TuringTest  paul's notes!
i was going to make my own, until i found this one and thought 'why bother?'

anonymous · Answer

@jeessicaaahh  it is a great cheat sheet ( i can say that because i did not make it) so use it to  your benefit. if you lose it google "paul's notes" and you will find lots of useful stuff for trig and also for future classes