#LHS#
Identity:
#color(red)(sin(A+B)=sinAcosB+cosAsinB)#
#sin(3x)=sin(x+2x)=sin(x)cos(2x)+cos(x)sin(2x)#
#(sin(x)cos(2x)+cos(x)sin(2x))/(sinxcosx)=>#
#(sin(x)cos(2x))/(sin(x)cos(x))+(cos(x)sin(2x))/(sin(x)cos(x))#
#(cancel(sin(x))cos(2x))/(cancel(sin(x))cos(x))+(cancel(cos(x))sin(2x))/(sin(x)cancel(cos(x)))#
#cos(2x)/cos(x)+sin(2x)/sin(x)#
Identities:
#color(red)(sin(2A)=2sin(A)cos(A))#
#color(red)(cos(2A)=2cos^2(A)-1)#
#(2cos^2(x)-1)/cos(x)+(2sin(x)cos(x))/sin(x)#
#2cos(x)-1/cos(x)+2cos(x)=4cos(x)-1/cos(x)#
Identity
#color(red)(1/cos(A)=sec(A))#
#->=4cos(x)-sec(x)#
#LHS-=RHS#