Question

How would i go about finding cos of 7pi/4 ? (And for sin to but if its the same process then cos is only needed and i'll connect the dots)

Answer 1

look at the last page of the attached cheat sheet.
find \(\frac{7\pi}{4}\) on the unit circle
the first coordinate is cosine, the second coordinate is sine

Answer 2

or you have to memorize a triangle and put it in the unit circle in the appropriate place

Answer 3

right \(\frac{\sqrt{2}}{2}\) and down \(\frac{\sqrt2}{2}\) so
\[\cos(\frac{7\pi}{4})=-\frac{\sqrt2}{2}\] and
\[\sin(\frac{7\pi}{4})=\frac{\sqrt2}{2}\]

Answer 4

Oh wow thanks, i feel dumb for not looking over the entire unit circle, for some reason i was thinking 7pi/4 was not on it.

Answer 5

all numbers are on it
sometimes you just have to keep going round and around

Answer 6

One thing, would
-\[-\sin7\pi/4 + 7\cos7\pi/4= 7\sqrt{2}/2 ?\]

Answer 7

no i don't think so

Answer 8

we have the numbers we need
you will get
\[\frac{\sqrt2}{2}+7\frac{\sqrt2}{2}=\frac{8\sqrt2}{2}=4\sqrt2\]

Answer 9

Oh thanks, i just realized this when looking at an example on the math program? didn't realize an invisible one (That is what it is right?)