Sine-cosine offset identity

As well as the identity that \sin^2\theta+\cos^2\theta\equiv1, there is another identity linking the \sin function with the \cos function:

\cos x\equiv\sin(x+90)

And, similarly, we can find that:

\sin x\equiv\cos(x-90)

Other derivatives

• \sin x\equiv\cos(90-x)\equiv\cos(x-90)
• \cos x\equiv\sin(90-x)\equiv\sin(x+90)
• \cos x=\sin(x+90)
• \sin x=\cos(x-90)