# Trig functions..Simplifying....

In 5, there is a preponderance of sin(x), so solve for $\cos^{2}(x)\;=\;1\;-\;\sin^{2}(x)$ and substitute. You will be left with a bunch of sines that you can handle.
In 6, there is a preponderance of cos(x), so solve for $\sin^{2}(x)\;=\;1\;-\;\cos^{2}(x)$ and substitute. You will be left with a bunch of cosines that you can handle.