两角和公式sin(A+B)=sinAcosB+cosAsinBsin(A-B)=sinAcosB-sinBcosAcos(A+B)=cosAcosB-sinA
倒数关系tanα·cotα=1sinα·cscα=1cosα·secα=1商的关系sinα/cosα=tanα=secα/cscαcosα/sinα=cotα
两角和与差的三角函数:sin(A+B)=sinAcosB+cosAsinBsin(A-B)=sinAcosB-cosAsinB?cos(A+B)=cosAco
万能公式推导sin2α=2sinαcosα=2sinαcosα/(cos^2(α)+sin^2(α))......*,(因为cos^2(α)+sin^2(α)