已知tanα=-1/2,求2sin^2α+sinα×cosα-3cos^2α的值
<p>问题：已知tanα=-1/2,求2sin^2α+sinα×cosα-3cos^2α的值<p>答案：↓↓↓<p class="nav-title mt10" style="border-top:1px solid #ccc;padding-top: 10px;">连红的回答：<div class="content-b">网友采纳 原式=（2sin^2a+sinacosa-3cos^2a)/(sin^2a+cos^2a) =(2tan^2a+tana-3)/(tan^2a+1) =(2*1/4-1/2-3)/(1/4+1) =-12/5
页:
[1]