cos(45∘+A)−cos(45∘−A)sin(120∘+A)–sin(120∘–A)= View Solution Prove that ·cos135∘−cos120∘cos135∘+cos120∘=3−2√2 View Solution Prove the following: (i)sinα+sin(α+2π3)+sin(α+4π3)=0 ...
(1)化简:cosA+cos(120°-A)+cos(120°+A).(2)求值:sin130°(1+3cot80°). 答案 (1)原式=cosA+2cos120°cos(-A)=cosA-cosA=0;(2)原式=sin130°(1+3cos80°sin80°)=2sin130°sin(80°+60°)sin80°=−2(cos270°−cos10°)sin80°=−2(0−cos10°)cos10°=2.相关...
【解析】(1)原式=cosA+2cos120°cos(-A)=cosA-|||--coS A=0-|||-;-|||-(2)原式=sin130°-|||-(1+-|||-V3cos80°-|||-sin80°-|||-2sin130°sin(80°+60°)-|||-sin80°-|||--2(cos270°-cos10°)-|||-sin80°-|||--2(0-cos10°)-|||-=2-|||-cos10° 结...
原式=cosa+cos120cosa+sin120sina+cos120cosa-sin120sina ==cosa+2cos120cosa =cosa+2×(-1/2)cosa =cosa-cosa =0
(1)原式=cosA+2cos120°cos(-A)=cosA-cosA=0;(2)原式=sin130°(1+ 3cos80° sin80°)= 2sin130°sin(80°+60°) sin80°= −2(cos270°−cos10°) sin80°= −2(0−cos10°) cos10°=2. (1)原式后两项利用和差化积公式化简,计算即可得到结果;(2)原式括号中利用同角三角函数间...
后面乘起来是COS 120 .. . 不会了 直角三角形没有钝角吧 0
原式=cosa+cos120cosa+sin120sina+cos120cosa-sin120sina ==cosa+2cos120cosa =cosa+2×(-1/2)cosa =cosa-cosa =0结果一 题目 化简cosa+cos(120-a)+cos(120+a) 答案 原式=cosa+cos120cosa+sin120sina+cos120cosa-sin120sina==cosa+2cos120cosa=cosa+2×(-1/2)cosa=cosa-cosa=0 结果二 题目 ...
百度试题 结果1 题目化简cosa+cos(120-a)+cos(120+a) 相关知识点: 试题来源: 解析 原式=cosa+cos120^0cosa+sin120^0sina+cos120^0cosa-sin120^0sina ==cosa+2cos120^0cosa =cosa+2×(-)cosa =cosa-cosa =0 反馈 收藏
没错。cos（-120）= cos120 但cos120=cos（180-60）=-cos60=-1/2 所以cos（-120）= -1/2 cos
化简:cosA+cos(120-A)+cos(120+A) 扫码下载作业帮搜索答疑一搜即得 答案解析 查看更多优质解析 解答一 举报 =cosa+cos120*cosa+sin120*sina+cos120*cosa-sin120*sina =cosa+2*cos120*cosa =0 解析看不懂?免费查看同类题视频解析查看解答 相似问题 ...