How do you verify the identity #sin(90+A)=cosA#?
1 Answer
Dec 21, 2016
Expand using the rule
#sin(90 + A) = cosA#
#sin90cosA + cos90sinA = cosA#
We know, by the unit circle, that
#1(cosA) + 0(sinA) = cosA#
#cosA = cosA#
#LHS = RHS#
Identity proved!
Hopefully this helps!