1.

If `cos(alpha-beta)=3sin(alpha+beta),t h e n1/(1-3sin2alpha)+1/(1-3sin2beta)=``1/2`(b) `(-1)/2`(c) `1/4`(d) `(-1)/4`A. `(1)/(2)`B. `(-1)/(2)`C. `(1)/(4)`D. (-1)/(4)`

Answer» Correct Answer - D
Put, `beta=0rArr tan alpha=(1)/(3)`
`rArr sin 2alpha=(2((1)/(3)))/(1+(1)/(9))=(3)/(5)`
`therefore (1)/(1-3sin 2alpha)+(1)/(1-3sin2beta)`
`=(1)/(1-3sin2alpha)+1=(1)/(1-(9)/(5))+1=(-1)/(4)`.


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