Question

( cot x cot y=2 )
( Rightarrow quad cos n cos y=2 sin n sin y )
-1
( =frac{cos (x+y)}{cos (x-y)}=frac{cos x cos y-sin x sin y}{cos x cos y+cos x sin y} )
By (1)( Rightarrow frac{text { sinnsing }}{3 text { sinnsing }} )
[
=1 / 3+frac{1-y}{2}
]

# 9) - Ls (2X + 2y). 33. ( (i) If cot x cot y = 2, show that cos (x + y)_1 cos(x - y) 3

Solution