Question

if sin 2a=square root of 2sina

Answer 1

$sin2a= \sqrt{2} \ sinA\\ \\ \Rightarrow 2\ sinA\ cosA= \sqrt{2} \ sin\ A\\ \\ \Rightarrow 2\ cosA= \sqrt{2} \\ \\ \Rightarrow cosA= \frac{\sqrt{2} }{2}= \frac{1}{ \sqrt{2} } \\ \\ \Rightarrow A= \frac{\pi}{4},\ -\frac{\pi}{4}$