Question #ce8c7

1 Answer
Nov 12, 2017

#-279(cos9x)^30*sin9x#

Explanation:

#y=(cos9x)^31#

Take natural logarithm both sides,

#Lny=31*Ln(cos9x)#

Take derivative both sides,

#(y')/y=31*(-9sin9x)/(cos9x)#

#y'=(-279sin9x)/(cos9x)*y#

=#(-279sin9x)/(cos9x)*(cos9x)^31#

=#-279(cos9x)^30*sin9x#