Question

1+tanx.tany/1-tanx.tany=cos(x-y).cos(x+y)

Answer 1

Answer:

correction RHS= cos(x-y) / cos(x+y)

Step-by-step explanation:

(1+tanxtany) / (1-tanxtany)= cos(x-y)/cos(x+y)

LHS

( 1+ sinxsiny/cosxcosy) / ( 1-sinxsiny/cosxcosy)

(cosxcosy+sinxsiny) / (cosxcosy)

= --------------------------------------------------

( cosxcosy-sinxsiny) / ( cosxcosy)

cosxcosy+sinxsiny

= ------------------------------

cosxcosy- sinxsiny

= cos(x-y) / cos(x+y)

= RHS

proved