sin2A+sin2(AB)+2sinAcosBsin(BA)= ?

options are

  1. sin2A
  2. sin2B
  3. cos2A
  4. cos2B

1 Answer
Aug 10, 2018

2.

Explanation:

sin2A+sin2(AB)+2sinAcosBsin(BA)=

sin2a+(sinacosbcosasinb)(sinacosbcosasinb)+2sinacosb(sinbcosacosbsina)=

sin2a+sin2acos2b2sinacosasinbcosb+cos2asin2b+2sinasinbcosacosb2cos2bsin2a=

sin2asin2acos2b+cos2asin2b=

sin2a(1cos2b+cot2asin2b)=

sin2asin2b(1+cot2a)=

sin2asin2b(csc2a)=

sin2asin2b(1sin2a)=

sin2b