Question

if A=60 degree and B=30 degree, verify that cos(A-B)=cosA cosB +sinA sinB

Answer 1

Answer:

$\cos(60 - 30 ) = \cos(60) \times \cos(30) + \sin(60) \times \sin(30) \\ \cos(30) = \frac{1}{2} \times \frac{ \sqrt{3} }{2} + \frac{ \sqrt{3} }{2} \times \frac{1}{2} \\ \frac{ \sqrt{3} }{2} = \frac{ \sqrt{3} }{4} + \frac{ \sqrt{3} }{4} \\ \frac{ \sqrt{3} }{2} = \frac{ 2\sqrt{3} }{4} \\ \frac{ \sqrt{3} }{2} = \frac{ \sqrt{3} }{2}$

Hence proved❕❕❕