已知sin(π-α)-cos(π+α)=根号2分之4,求sin(π+α)+cos(3π-α)的值_数学解答

已知sin(π-α)-cos(π+α)=根号2分之4,求sin(π+α)+cos(3π-α)的值

人气：455 ℃　时间：2019-10-14 02:08:44

解答

化简后发现右式与左式为相反数,即右式=-√2/4
sin(a+b)=sinacosb+cosasinb
sin(a-b)=sinacosb-cosasinb
cos(a+b)=cosacosb-sinasinb
cos(a-b)=cosacosb+sinasinb