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\begin{array} { l } { \text { Prove that } } \\ { \frac { \sin ( x + y ) } { \sin ( x - y ) } = \frac { \tan x + \tan y } { \tan x - \tan y } } \end{array} |
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Answer» sin(x+y)=sinxcosy +cosxsinysin(x-y) =sinxcosy-cosxsinyNow sin(x+y)/sin(x-y) = sinxcosy +cosxsiny / sinxcosy-cosxsinyDividing numerator and denominatorby cos x cosy and solving we gettanx+ tany /tanx -tany thanks |
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