If 3*tanx*tany=1 then show that 2cos (x+y)=cos(x-y)
karan patel , 7 Years ago
Grade 11
Trigonometry> If 3*tanx*tany=1 then show that 2cos (x+y...
1 Answers
Arun
Last Activity: 7 Years ago
3 sinx siny= cosx cosy
now,
2 sinx siny= cosx cosy –sinx siny
cos(x –y) –cos(x+y) = cos(x+y)
now cos(x –y)= 2 cos(x+y)
hence proved
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