倍角公式是那些?万能公式是那些?

Question

倍角公式是那些?万能公式是那些?

Answer 1

倍角公式sin(2α)=2sinα·cosα=2/(tanα+cotα) cos(2α)=(cosα)^2-(sinα)^2=2(cosα)^2-1=1-2(sinα)^2 tan(2α)=2tanα/(1-tan^2α) 万能公式sin(a)= (2tan(a/2))/(1+tan^2(a/2)) cos(a)= (1-tan^2(a/2))/(1+t...