Got this question in textbook assignments:
Prove the cofunction identity using the addition and subtraction formulas.
20. cot (pi/2 - u) = tan u
so to my knowledge, I turn it into:
1 / tan (pi/2 - u) and try to apply subtraction formula but then tan pi/2 isn't defined is it? because 1/0 isn't defined. Is this the case?
[EDIT] I've also run into this now and don't want to spam the forums so I will post here, prove:
sin(pi/2 - x) = sin(pi/2 + x)
I start with RHS = sin(pi/2) cos x + cos (pi/2) sin x
= (1) cos x + (0) sin x
= cos x
Haha this is probly also simple but alas it eludes me...