Review the steps of the proof of the identity sine (a minus startfraction 3 pi over 2 endfraction) = cosine a. Sine (a minus startfraction 3 pi over 2 endfraction) step 1: = sine a cosine (startfraction 3 pi over 2 endfraction) minus cosine a sine (startfraction 3 pi over 2 endfraction) step 2: = (sine a) (0) + cosine a (negative 1) step 3: = (sine a) (0) + (1) (cosine a) step 4: = 0 + cosine a step 5: cosine a at which step was an error made?.
