1.

Let `f(theta)=cottheta/(1+cottheta)` and `alpha+beta=(5pi)/4` then the value ` f(alpha)f (beta)` isA. `(1)/(2)`B. `-(1)/(2)`C. 2D. none of these.

Answer» Correct Answer - A
`f(beta)=f((5pi)/(4)-alpha)=(cot((5pi)/(4)-alpha))/(1+cot((5pi)/(4)-alpha))`
`=(1)/(1+(1-tanalpha)/(1+tan alpha))=(1+tan alpha)/(2)`
As `f(x)=(cotalpha)/(1+cotalpha)=(1)/(1+tan alpha)`, we have
`f(alpha)f(beta)=(1)/(2)`


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