MCQ
The value of $cos\, 255^o + sin\, 195^o$ is
- A$\frac{{\sqrt 3 - 1}}{{2\sqrt 2 }}\,$
- B$\frac{{\sqrt 3 - 1}}{{\sqrt 2 }}\,$
- ✓$-\frac{{\sqrt 3 - 1}}{{\sqrt 2 }}\,$
- D$\frac{{\sqrt 3 + 1}}{{\sqrt 2 }}\,$
$ = \,\cos \,({270^o}\, - \,{15^o})\, + \,\sin \,({180^o} + {15^o})$
$ = \, - \,\sin \,{15^o}\, - \,\sin \,{15^o}$
$ = \, - \,2\,\sin \,{15^o}\, = \, - \,2\left( {\frac{{\sqrt 3 - 1}}{{2\sqrt 2 }}} \right)\, = \, - \,\left( {\frac{{\sqrt 3 - 1}}{{\sqrt 2 }}} \right)$
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Statement $-1 :$ $gof $ is differentiable at $x=0$ and its derivative is continuous at that point
Statement $-2 :$ $gof $ is twice differentiable at $x=0 $