# Thread: trig functions

1. ## trig functions

Find an exact solution to the equation.

1=12cos(3x+1)-5

ok i thought i knew how to do this one, i came up with

x= (arccos(1/2)-1)/3

but it was wrong, if someone could tell me what i did wrong that would be awesome...thanks

mathlete

2. Originally Posted by mathlete
Find an exact solution to the equation.

1=12cos(3x+1)-5

ok i thought i knew how to do this one, i came up with

x= (arccos(1/2)-1)/3

but it was wrong, if someone could tell me what i did wrong that would be awesome...thanks

mathlete
$\displaystyle 12 \cos (3x + 1) - 5 = 1$

$\displaystyle \Rightarrow \cos (3x + 1) = \frac 12$

$\displaystyle \Rightarrow 3x + 1 = \frac {\pi}3 + 2 k \pi, \mbox{ or } \frac {5 \pi}3 + 2n \pi$, for $\displaystyle n,k \in \mathbb{Z}$

now continue