I have to find the two solutions for;
$\displaystyle
cos(2t)=-0.75, \pi < t < 2 \pi
$
i have sketched a graph, but am unsure how to get the values mathematically?
Many thanks
$\displaystyle \pi < t < 2\pi$
$\displaystyle 2\pi < 2t < 4\pi$
$\displaystyle \cos(2t) = -0.75$
$\displaystyle 2t = 2\pi + \arccos(-0.75)$
$\displaystyle t = \pi + \frac{1}{2}\arccos(-0.75)$
$\displaystyle 2t = 4\pi - \arccos(-0.75)$
$\displaystyle t = 2\pi - \frac{1}{2}\arccos(-0.75)$