# Thread: Trigonometric Methods

1. ## Trigonometric Methods

Hi all,
I am having some problems with my trig revision. It's been such a long time since I've done this I have completly forgot exactly what I am supposed to be doing with this! If someone could walk me through the first question I hope I'll be able to pick it up from there!

The Power P in an alectrical circuit is given by P = v squared/R

Find the power in terms of V, R and Cos2t when v = VCost

Thanks!
MM

2. $\displaystyle P = \frac{v^2}{R} =\frac{(V \cos t)^2}{R}=$$\displaystyle \dfrac{V^2 \frac{1+\cos 2t}2}{R} = \dfrac{V^2(1+ \cos 2t)}{2R}$ I have used the relation $\displaystyle \cos 2t = 2 \cos^2 t - 1$