Cosine and Sine Identities with Dihedral Transformations
Cosine and Sine Identities with Dihedral Transformations
The relation between certain cosine and sine identities and certain rotations and reflections in the plane are exhibited. For example, is the same as , which is the (90°) clockwise rotation, , of the point .
(cos(t+π/2),sin(t+π/2))
(-sin(t),cos(t))
π/2
(x,y)↦(-y,x)
(cos(t),sin(t))