Question

ff. Cos alpha /a =sin alpha /b then show that
a cos2 alpha+ b sin 2 alpha = a​

Answer 1

Answer:

sorry for handwriting, but that's your answer

Answer 2

Answer:

Step-by-step explanation:

Given,

$\frac{cos\alpha }{a} =\frac{sin\alpha }{b}$

$multiply\ \:2sin\alpha \: on\: both \:sides$

$\frac{(2sin\alpha) cos\alpha }{a} =\frac{(2sin\alpha )sin\alpha }{b} \:\:\:\:\:\:\:\:\\\frac{sin2\alpha }{a} =\frac{2sin^{2}\alpha }{b}\\bsin2\alpha=a2sin^{2}\alpha\\bsin2\alpha=a(1-cos2\alpha ) \: \\bsin2\alpha=a-acos2\alpha \\acos2\alpha+bsin2\alpha=a$