If and lies in the first quadrant

MATHEMATICS · Single correct · A Level · Mathematics · Trigonometry · Trigonometry

Problem

If

\cos 2x=\dfrac35

and

x

lies in the first quadrant, what is

\sin x

? (a)

\dfrac{2}{\sqrt5}

(b)

\sqrt{\dfrac{3}{10}}

(c)

\dfrac{\sqrt5}{5}

(d)

\sqrt{\dfrac{2}{5}}

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