Question

用图象法解方程组2x-y=1，x+y=5 要画出图

Answer 1

图像自己画吧，两个一次函数
分别是y=2x-1和y=-x+5
由图像看出交点是(2,3)
所以x=2,y=3

Answer 2

左边=(sina/cosa*sin2a/cos2a)/(sin2a/cos2a-sina/cosa)-√3(cos2a-sin2a)
上下乘cosacos2a
=(sinasin2a/(sin2acosa-sinacos2a)-√3(cos2a-sin2a)
=(sinasin2a)/sin(2a-a)-√3cos2a
=sin2a-√3cos2a
=2(sin2a*1/2-cos2a√3/2)
=2(sin2acosπ/3-cos2asinπ/3)
=2sin(2a-π/3)
=右边
命题得证