# Trig equations

• Oct 23rd 2008, 02:52 PM
IDontunderstand
Trig equations
How many solutions exist for the equation 3Cos 2x=-3 in the interval 0<=x<=2Pi The 2 confuses me. How do I adjust for that? Thanks
• Oct 23rd 2008, 03:14 PM
skeeter
$3\cos(2x) = -3$

$\cos(2x) = -1$

since $0 \leq x \leq 2\pi$ , then $0 \leq 2x \leq 4\pi$

$2x = \pi$

$x = \frac{\pi}{2}$

$2x = 3\pi$

$x = \frac{3\pi}{2}$