derivative?

Question

what is the derivative of the following? (begin square root sign) cos(7n) (end square root sign) - arctan(2n)

 

thanks in advance

Answer 1

Let's use x instead, since n usually is used as an integer-valued variable.

 

d/dx √(cos 7x) - tan^-1 2x

 

= [(cos 7x)^-1/2/2](-sin 7x)(7) + [1/(1+(2x)²)](2)

 

= (-7/2)(cos 7x)^-1/2sin 7x + 2/(1 + 4x²)