1.

Choose the correct answer in each of the following questions: If `2cos 3 theta=1 " then " theta=?`A. `10^(@)`B. `15^(@)`C. `20^(@)`D. `30^(@)`

Answer» Correct Answer - C
`2cos3theta=1rArr cos3theta=(1)/(2)=cos60^(@)rArr3theta=60^(@)rArr theta=20^(@).`


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