Prove:cos inverse(cos alpha+cos beta/1+cos alpha cos beta)=2tan inverse(tan alpha/2 tan beta/2 Share with your friends Share 21 Manbar Singh answered this RHS = 2 tan-1tanα2 . tanβ2=cos-11 - tan2α/2 . tan2β/21 + tan2α/2 . tan2β/2=cos-1cos2α/2 . cos2β/2 - sin2α/2 . sin2β/2cos2α/2 . cos2β/2 + sin2α/2 . sin2β/2=cos-12cos2α/2 . 2cos2β/2 - 2sin2α/2 . 2sin2β/22cos2α/2 . 2cos2β/2 + 2sin2α/2 . 2sin2β/2=cos-11 + cos α1 + cos β - 1 - cos α1 - cosβ1 + cos α1 + cos β+ 1 - cos α1 - cosβ=cos-1cos α + cos β1 + cos α . cos β=LHS 48 View Full Answer
