1) What kind of triangle is ABC if for his angles we have:(adsbygoogle = window.adsbygoogle || []).push({});

sin[2*(alfa)]=2sin[beta]*cos[gama]

2) If acos[alfa] + bsin[alfa]=acos[beta]+b[sin[beta] , prove that sin(alfa+beta)=2ab/(a^2+b^2)

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# Please help, Contest questions

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