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3.Trigonometrical Ratios, Functions and Identities
easy
The value of $\cos A - \sin A$ when $A = \frac{{5\pi }}{4},$ is
A
$\sqrt 2 $
B
$\frac{1}{{\sqrt 2 }}$
C
$0$
D
$1$
Solution
(c) $\cos A – \sin A = \cos \frac{{5\pi }}{4} – \sin \frac{{5\pi }}{4},\left( \because {A = \frac{{5\pi }}{4}} \right)$
$ = – \cos \frac{\pi }{4} + \sin \frac{\pi }{4} = – \frac{1}{{\sqrt 2 }} + \frac{1}{{\sqrt 2 }} = 0$.
Standard 11
Mathematics
