यदि `cos ""x/2. cos ""(x)/( 2 ^(2)) . cos "" (x )/( 2 ^(3)) ... oo = (sin x )/(x)` `(1)/( 2 ^(2))sec ^(2) ""(x)/(2) + (1)/(2 ^(4)) sec ^(2) "" (x)/(2 ^(2)) +(1)/(2 ^(6)) (1)/(2 ^(6)) (x)/(2 ^(3)) +...oo` का मान ज्ञात कीजिए।

Answer

`cosec ^(2) x - (1 //x ^(2))`