Derivatives - Properties and Formulas

Question

If f(x) = 3sin(x) + 5cos(x) then,

f'(4) =

Answer 1

f(x) = 3sinx +5cosx

f'(x) = 3cosx -5sinx

f'(4) = 3cos4 -5sin4

if 4 means 4 degrees

then

f'(4) = 3cos4-5sin4 = about 2.644

but if 4 means 4 radians

f'(4) =3cos4-5sin4

= 3cos(4x180/pi)-5sin(4x180/pi)

= 3cos(720/pi)-5(720/pi)

= -1.961 - 2.939

=about - 4.9