根号3sinx/2+cosx/2 =2(根号3/2sinx/2+1/2cosx/2) =2(cos30°sinx/2+sin30°cosx/2) =2sin(x/2+30°)为什么最后得数等于2sin(x/2+30°) X是怎么留下来的.还有30°是怎么留下来的.
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![根号3sinx/2+cosx/2 =2(根号3/2sinx/2+1/2cosx/2) =2(cos30°sinx/2+sin30°cosx/2) =2sin(x/2+30°)为什么最后得数等于2sin(x/2+30°) X是怎么留下来的.还有30°是怎么留下来的.](/uploads/image/z/1700431-7-1.jpg?t=%E6%A0%B9%E5%8F%B73sinx%2F2%2Bcosx%2F2+%3D2%28%E6%A0%B9%E5%8F%B73%2F2sinx%2F2%2B1%2F2cosx%2F2%29+%3D2%28cos30%C2%B0sinx%2F2%2Bsin30%C2%B0cosx%2F2%29+%3D2sin%28x%2F2%2B30%C2%B0%29%E4%B8%BA%E4%BB%80%E4%B9%88%E6%9C%80%E5%90%8E%E5%BE%97%E6%95%B0%E7%AD%89%E4%BA%8E2sin%28x%2F2%2B30%C2%B0%29+X%E6%98%AF%E6%80%8E%E4%B9%88%E7%95%99%E4%B8%8B%E6%9D%A5%E7%9A%84.%E8%BF%98%E6%9C%8930%C2%B0%E6%98%AF%E6%80%8E%E4%B9%88%E7%95%99%E4%B8%8B%E6%9D%A5%E7%9A%84.)
根号3sinx/2+cosx/2 =2(根号3/2sinx/2+1/2cosx/2) =2(cos30°sinx/2+sin30°cosx/2) =2sin(x/2+30°)为什么最后得数等于2sin(x/2+30°) X是怎么留下来的.还有30°是怎么留下来的.
根号3sinx/2+cosx/2 =2(根号3/2sinx/2+1/2cosx/2) =2(cos30°sinx/2+sin30°cosx/2) =2sin(x/2+30°)
为什么最后得数等于2sin(x/2+30°)
X是怎么留下来的.还有30°是怎么留下来的.
根号3sinx/2+cosx/2 =2(根号3/2sinx/2+1/2cosx/2) =2(cos30°sinx/2+sin30°cosx/2) =2sin(x/2+30°)为什么最后得数等于2sin(x/2+30°) X是怎么留下来的.还有30°是怎么留下来的.
见三角函数公式:
sin(x+y)=sinxcosy+cosxsiny
这个直接根据公式而来 cosasinb+sinbcosa =sin(a+b) cos30°=根号3/2 sin30°=1/2
加号两边都提取一个2就得到括号里的式子,再根据sin30°=1/2,,,cos30°=√3/2替代括号里的1/2和√3/2就变成了2(sinx/2cos30°+cosx/2sin30)=2(sinx/2+cos30°)
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