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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` |
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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`. |
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