1-余弦=cos0°-cosα= - 2sin(0°+α)/2*sin(0°-α)/2= -2sinα/2*sin(-α)/2=2sinα/2*sinα/2=2sin²α/2
正弦=sinα=2sinα/2*cosα/2
区别:
1-余弦=2sinα/2*sinα/2
正弦=2sinα/2*cosα/2
(1-余弦):正弦=2sinα/2*sinα/2:2sinα/2*cosα/2=sinα/2:cosα/2=tan(α/2)
1-余弦=cos0°-cosα= - 2sin(0°+α)/2*sin(0°-α)/2= -2sinα/2*sin(-α)/2=2sinα/2*sinα/2=2sin²α/2
正弦=sinα=2sinα/2*cosα/2
区别:
1-余弦=2sinα/2*sinα/2
正弦=2sinα/2*cosα/2
(1-余弦):正弦=2sinα/2*sinα/2:2sinα/2*cosα/2=sinα/2:cosα/2=tan(α/2)