已知3sinα=-cosα,求1+sinαcosα的值(高一数学)急!
问题描述：
已知3sinα=-cosα,求1+sinαcosα的值(高一数学)急!
答
3sinα=-cosα两边取平方,9(sinα)^2 = (-cosα)^29(sinα)^2 = (cosα)^2两边同时加上(sinα)^29(sinα)^2 +(sinα)^2 = (cosα)^2 +(sinα)^210(sinα)^2 =1(sinα)^2 =1/10...(1)1+sinαcosα...(将3sinα=-cosα...