Example determines the first four derivatives for following.
y = cos x
Solution: Again, let's just do some derivatives.
y = cos x
y′ = - sin x
y′′ = - cos x
y′′′ = sin x
y( 4) = cos x
Note as well that cosine (and sine) will repeat each four derivatives. The other four trig functions will not demonstrate this behavior. You may desire to take a few derivatives to convince yourself of this.