If cos(x-y)=3cos(x+y) Find cotxcoty. (A)0 (B)1 (C)2 (D)3 If there is an any NSTSE 11 pcm student tell me.
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cos(x-y) = 3cos(x+y)
cosx.cosy+sinx.siny = 3(cosx.cosy-sinx.siny)
cosx.cosy+sinx.siny = 3cosx.cosy-3sinx.siny
4sinx.siny = 2cosx.cosy
cosx.cosy/sinx.siny = 4/2
cotx.coty = 2
cosx.cosy+sinx.siny = 3(cosx.cosy-sinx.siny)
cosx.cosy+sinx.siny = 3cosx.cosy-3sinx.siny
4sinx.siny = 2cosx.cosy
cosx.cosy/sinx.siny = 4/2
cotx.coty = 2
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