Question

cos(2θ)=cos^2(θ)−sin^2(θ)?

Answer 1

Yup. Remember the identity \(\cos(a+b) = \cos a\cos b - \sin a \sin b\)? Just let \(a = b = \theta\)

Answer 2

http://www.biology.arizona.edu/biomath/tutorials/trigonometric/graphics/Trigidenteqn6.gif

Answer 3

\[\cos2\theta=\cos(\theta+\theta)\]
\[=( cos \theta*\cos \theta)-(\sin \theta*\sin \theta)\]
\[=\cos ^{2}\theta-\sin ^{2}\]

Answer 4

lol its sin ^2 theta

Answer 5

then why does r^2 [cos 2theta]=1

Answer 6

at r=1 and \[\theta=0\]
r^2 [cos 2theta] would be 1

Answer 7

hey, if @ParthKohli says its "yup", then its yup !

Answer 8

lol -_-