摘要
公式:sin(α+β)sin(α-β)=sin^2α-sin^2β(*)
证明:左边=(sinαcosβ+cosαsinβ)(sinαcosβ-cosαsinβ)=(sinαcosβ)^2-(cosαsinβ)^2=sin^2αcos^2β-cos^2αsin^2β=sin^2α(1-sin^2β)-cos^2sin^2β=sin^2α-sin^2αsin^2β-cos^2αsin^2β=sin^2α-(sin^2α+cos^2α)sin^2β=sin^2α-sin^2β=右边.得证.
出处
《中学生数理化(高一使用)》
2011年第6期16-16,共1页
Maths Physics & Chemistry for Middle School Students(Senior High School Edition)