1.

Let `f(theta)=sin theta(sin theta +sin 3 theta). " Then " f(theta)`A. ` ge 0," only when " theta ge 0`B. `le 0," for all real " theta`C. `ge 0," for all real " theta`D. `le 0," only when " theta le 0`

Answer» Correct Answer - C
It is given,
`f(theta)=sin theta(sin theta + sin 3 theta )`
`=(sin theta +3 sin theta -4 sin^(3) theta) sin theta`
`= (4 sin theta -4 sin^(3) theta) sin theta=sin^(2) theta (4-4 sin^(2) theta )`
` =4sin^(2) theta cos^(2) theta =(2 sin theta cos theta )^(2)`
`=(sin 2 theta)^(2) ge 0`
which is true for all `theta`.


Discussion

No Comment Found