MCQ
The value $\cos 105^\circ + \sin 105^\circ $ is
  • A
    $\frac{1}{2}$
  • B
    $1$
  • C
    $\sqrt 2 $
  • $\frac{1}{{\sqrt 2 }}$

Answer

Correct option: D.
$\frac{1}{{\sqrt 2 }}$
d
(d) $\cos 105^\circ + \sin 105^\circ = \cos (90^\circ + 15^\circ ) + \sin (90^\circ + 15^\circ )$

$= \cos 15^\circ - \sin 15^\circ $

$= \frac{{\sqrt 3 + 1}}{{2\sqrt 2 }} - \frac{{\sqrt 3 - 1}}{{2\sqrt 2 }} $

$= \frac{2}{{2\sqrt 2 }} = \frac{1}{{\sqrt 2 }}$.

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free