1.

`sin((1)/(2)cos^(-1).(4)/(5))` is equal toA. `-(1)/(sqrt(10))`B. `(1)/(sqrt(10))`C. `-(1)/(10)`D. `(1)/(10)`

Answer» Correct Answer - B
`sin ((1)/(2)cos^(-1).(4)/(5))`
Now ,put `(4)/(5)=cos 2theta`
`therefore sin((1)/(2)xx2theta)=sintheta=sqrt((1-cos2theta)/(2))`
`=sqrt((1-(4)/(5))/(2))=sqrt((1)/(5xx2))=(1)/(sqrt(10))`.


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