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**slapmaxwell1** well if i was solving for theta, cos 5theta = -1 then i would say con inverse of (-1) = 5 theta, and then divide both sides by 5 to get theta, but i dont see the connection? im still missing the big picture....oh and yeah i tried the double angle, i used double angle to solve and figure out with cos 15 was...the 36 is really throwing me off, maybe if i add it something and then subtract it, i could try to use a difference formula...one of the guys in class said something about using the quadratic equation to solve the problem??? i really dont see the connection there...