Question

Given tan theta = -2, find cos 2theta

Answer 1

\[\dfrac{-1}{0.5} = -2\]So I think we need to find a \(\theta\) such that \(\sin \theta = -1\) and \(\cos \theta = 0.5\)

Answer 2

or you can use the formula for cos 2theta in terms of tan theta

Answer 3

\(\cos 2\theta =\dfrac{1-\tan^2 \theta}{1+\tan^2 \theta}\)

Answer 4

\[ \tan \theta = \dfrac{\sin(2\theta)}{\cos(2\theta) + 1}\]Right? :-\

Answer 5

yes

Answer 6

could you get cos 2theta now ?