lim(x---1)[sin^2(x)-sin^2(1)]/[x-1]=? University Advanced Mathematics, seek advice

lim(x---1)[sin^2(x)-sin^2(1)]/[x-1]=? University Advanced Mathematics, seek advice

be careful
lim(x->a) [f(x) -f(a)] /(x-a)
Is equal to f '(a)
So here, f (x) = sin ^ 2 (x)
lim(x->1) [sin^2(x)-sin^2(1)]/ [x-1] = f '(1)
And f (x) = sin ^ 2 (x)
f '(x)= 2sinx *cosx=sin2x
So get
Original limit
= f '(1)
= sin2