„Hornafræði“: Munur á milli breytinga

:<math>\sin \left(x-y\right)=\sin x \cos y - \cos x \sin y \,</math>

:<math>\cos \left(x-y\right)=\cos x \cos y + \sin x \sin y \,</math>

 

:<math>\sin^2 x + \cos^2 x = 1\,</math>