Product Rule with Trig Functions
For y=tanxsinx, we need to use the product rule since we have a product of two functions:
dxdy=tanx⋅dxd(sinx)+sinx⋅dxd(tanx)
Substituting the derivatives:
dxdy=tanx⋅cosx+sinx⋅sec2x
Simplifying:
=cosxsinx⋅cosx+sinx⋅sec2x=sinx+sinxsec2x=sinx(1+sec2x)
For y=cos4t−sin4t, we use the power rule for each term:
dxdy=4cos3t⋅(−sint)−4sin3t⋅cost=−4cos3tsint−4sin3tcost
Factoring out common terms and using trig identities:
=−4costsint(cos2t+sin2t)=−4costsint=−2(2sintcost)=−2sin2t
Simplify smartly: Trig identities like sin2t+cos2t=1 and sin2t=2sintcost can dramatically simplify your answers!