证明2sin(a+b)cos(a-b)=sin2a+sin2b_数学解答

证明2sin(a+b)cos(a-b)=sin2a+sin2b

人气：432 ℃　时间：2020-09-28 02:03:14

解答

2sin(a+b)cos(a-b)=2(sinacosb+sinbcosa)(cosacosb+sinasinb)=2(sinacosacos^2b+sin^2asinbcosb+sinbcosbcos^2a+sin^2bsinacosa)=2(sinacosa+sinbcosb)=sin2a+sin2b