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3. trignometrical ratios,functions and identities — MATHS STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 ScienceMATHS3. trignometrical ratios,functions and identities1 Mark
MCQ
If $cos\, (\alpha + \beta ) = 0$ then $sin \,(\alpha + 2\beta ) =$
  • ✓
    $sin\, \alpha$
  • B
    $- sin\, \alpha$
  • C
    $cos\, \beta$
  • D
    $- cos\, \beta$
✓

Answer

Correct option: A.
$sin\, \alpha$
a
$\alpha + \beta = \frac{\pi}{2} \Rightarrow\, \beta = \frac{\pi}{2} -\alpha$ $\Rightarrow \,sin\, (\alpha + 2\beta ) = sin\, (\alpha + \pi - 2\alpha ) = sin\, (\pi -\alpha ) =\, sin\, \alpha$ 

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