Solve for x:
cos (x) = 3x/(2pi)
The asnwer is pi /3 but how is it solved algebraically???
Numerical methods are iterative methods, such as the Bisection Method or Newton's Method. Google them.
Like I said, this point of intersection can NOT be solved algebraically, because you have a trigonometric function on one side and a polynomial function on the other. There is no way to combine them...