For each of the following values of cos theta, determine the radian values of theta if theta is btwn pi and 2pi.

- 1/2 MY answer is theta= pi/3 but textbook says it is 4pi/3....and i have NO idea why...I have this same issue with other questions of this type, I get the RAA right, but not the coefficient

Also,

Terminal arm of an angle in standard position passes thru each of the following points. Find radian value of angle in internal [0, 2pi].

point (-7, 8)

I got sin theta= y/r

= 8/10.63 (using pythagorean theorem)

theta = .752476694 but textbook answer is 2.25....once again, i have no idea how they came to this.

When do i use sin^-1 vs. sin by itself? o.0 HELP!! Unit test tmrw afternoon!!