Originally Posted by

**jonnygill** i made this substitution, and used the quadratic formula to find possible values of x. i ignored the solution where x=-6, since we will be taking the sqrt of a negative number, and i'm not interested in non-real solutions for this problem. so, i got $\displaystyle cos\Theta=\pm\sqrt\dfrac{5}{9}$.

i solved for Theta and got... $\displaystyle \Theta=138.1897$ OR $\displaystyle \Theta=41.8103$

i plugged both of these into the original equation and neither one worked!!

what did i do wrong???