derivatives of trig functions

[Truscuit]

#1.show that the gragh of y=secx and y=cosx have no horizontal tangents.
#2.find the points on the curve y=tanx, ?/2<x<?/2, where the tangent is parrallel to the line y=2x.
#3. use the identity sin2x=2sinxcosx to find the derivative of sin2x. then use the identity cos2x=cos^2 x-sin^2 x to express that derivative in terms of cos2x.

 

[tkhunny]

#1 - Please provide the definition of a Tangent. Be VERY specific.

#2 - Well, do it. What is (d/dx)tan(x)?

#3 - It appears to be a rather thorough road map for you to follow. Follow it.

Let's see what you get.