若cos2a/sin（a-π/4)=-√2/2,求cosa+sina的值.
<p>问题：若cos2a/sin（a-π/4)=-√2/2,求cosa+sina的值.<p>答案：↓↓↓<p class="nav-title mt10" style="border-top:1px solid #ccc;padding-top: 10px;">姜超的回答：<div class="content-b">网友采纳 cos2a/sin（a-π/4)=-√2/2,sin(π/2-2a)/sin（a-π/4)=-√2/2,-sin(2a-π/2)/sin（a-π/4)=-√2/2,[-2sin（a-π/4)cos（a-π/4)）/sin（a-π/4)=-√2/2,-2cos（a-π/4)）=-√2/2,-2[cosacosπ/4+sina...
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