Question

prove fast class 11​

Answer 1

Answer:

I am still class 8. I just got like this: (cosA-cosB)^2  -cos(A+B)=sin^2  (A+B)

I can't simplify that.

Answer 2

the following formulas have been used

$\sin( \alpha + \beta ) = \sin( \alpha ) \cos( \beta ) + \cos( \alpha ) \sin( \beta )$

$\cos( \alpha + \beta ) = \cos( \alpha ) \cos( \beta ) - \sin( \alpha ) \sin( \beta )$

$1 - { \cos( \alpha ) }^{2} = { \sin( \alpha ) }^{2}$

${(a + b)}^{2} = {a}^{2} + {b}^{2} + 2ab$