another two that i am stuck:

cos4x-7cos2x=8 with interval [0,2pi)

and tan^2(theta) + Tan (theta) -12 with the same interval.

for this one i have so far:

tan=-4 and tan=3 meaning they are not special right triangles...so i have to use the calculator...but my teacher said that theres a way to graph it and the points of intersection are the answers