tan9x = (tan7x + tan2x)/(1 - tan7x*tan2x)here its given1 - tan2x*tan7x= 0impliestan9x = infinitysincetan9x = (3tan3x - tan^3(3x))/(1 - 3tan^2 (3x)) = infinityimplies1- 3tan^2(3x) = 0impliestan3x = 1/sqrt(3). #question..