Question

Solve this equation: 2cosx +5 = 4

Answer 1

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

Answer 2

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

Answer 3

It's both :3

Answer 4

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.

Answer 5

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

Answer 6

oh okay thanks everyone!

Answer 7

^_^