Solve this equation: 2cosx +5 = 4

Question

psymon · Answer

If you know your unit circle well enough, then this problem isn't bad. You want to isolate cosx first and see what you end up with. In this case, you'll have cosx = to something very convenient that you may be able to recognize or look on your unit circle for. So just start by getting cosx by itself

avanti · Answer

cosx = -1/2 but how do i know if its 2π/3 or 4π/3?

psymon · Answer

It's both :3

psymon · Answer

In trig you have to start getting used to the idea that, depending on the problem, you could have 4, 8, 12 answers and anywhere in between depending on the period of the function and the interval.

anonymous · Answer

It is like x^2 = 4 ... the answer is x = 2 or x = -2... Same kind of thing here.

avanti · Answer

oh okay thanks everyone!

psymon · Answer

^_^