MCQ
The minimum value of $\cos \theta + \sin \theta $ is
- A$0$
- ✓$ - \sqrt 2 $
- C$1/2$
- D$\sqrt 2 $
Since $ - 1 \le \cos \left( {\theta - \frac{\pi }{4}} \right) \le 1$
==> $ - \sqrt 2 \le \sqrt 2 \cos \left( {\theta - \frac{\pi }{4}} \right) \le \sqrt 2 $
Thus, the minimum value of $f(x)$ is $ - \sqrt 2 $.
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$y = a\,{\cos ^2}x + 2b\,\sin x\cos x + c\,{\sin ^2}x$
and $z = a{\sin ^2}x - 2b\sin x\cos x + c{\cos ^2}x,$ then