已经知道COSX的值以及X的区间怎么求SINX和TANX
\u82e5sinx+cosx=tanx\uff0c\u5219x\u7684\u4e00\u4e2a\u503c\u7684\u6240\u5728\u533a\u95f4\u4e3a\uff08\uff09\u8fd9\u4e2a\u5148\u770b\u7b54\u6848,\u5168\u662f\u57280\u5230\u220f\uff0f2\u4e4b\u95f4\uff0c\u90a3\u4e48\u5c31\u53ef\u4ee5\u5730\u51fa
sinx+cosx\u57281\u5230\u6839\u53f72\u4e4b\u95f4\uff0e
\u90a3\u4e48\u663e\u7136tanx\u7684\u503c\u57281\u5230\u6839\u53f72\uff0c\u4e8e\u662fx\u4e00\u5b9a\u5927\u4e8e\u220f\uff0f4\uff0c\u6392\u9664A,B
tan.\u220f\uff0f3=\u6839\u53f73\uff0c\u5927\u4e8e\u6839\u53f72\uff0c\u90a3\u4e48\u7531\u4e8etanx\u57280\u5230\u220f\uff0f2\u4e4b\u95f4\u662f\u589e\u51fd\u6570\uff0c\u4e8e\u662fD\u4e2dx\u7684\u6240\u6709\u53d6\u503c\u90fd\u662f\u5927\u4e8e\u6839\u53f72\u7684\uff0c\u6392\u9664D
\u56e0\u6b64\u9009c
\u89e3\uff1a\u2235sinx+cosx=1/5..........(1)
\u2234(sinx+cosx)²=1/25
==>sinxcosx=-12/25..........(2)
\u628a(1)\u4ee3\u5165(2)\u6574\u7406\u5f9725sin²x-5sinx-12=0
==>(5sinx-4)(5sinx+3)=0.........(3)
\u22350\uff1cx\uff1c\u03c0\uff0csinxcosx=-12/25\uff1c0
\u2234sinx\uff1e0\uff0ccosx\uff1c0
\u2234\u7531(3)\u5f975sinx-4=0
==>sinx=4/5
\u2234\u7531(2)\u5f97cosx=-3/5
\u2234tanx=sinx/cosx=(4/5)/(-3/5)=-4/3\u3002
用同角三角函数基本关系式公式
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