Discuss with colleagues and IITians
solve the equation Cosa+sin2a+cos3a=0
2 Answers
Rinkoo Gupta
(cosa+cos3a)+sin2a=0
2cos2a.cosa+2sinacosa=0
2cosa(cos2a+sina)=0
=> cosa=0 or cos2a+sina=0
=>a=pi/2 or 1-2sin^2a+sina=0
2sin^2a-sina-1=0
sina={1+-sqrt(1-4(2)(-1))}/2(2)
=>sina=1,-1/2
=>a=pi/2 and 7pi/6
hence a=pi/2,7pi/6
Thanks & regards
Rinkoo Gupta
AskIITians Faculty
Arun Kumar
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