設(shè)所求向量c=(m,n),
|c|=√（m^2+n^2)=1,
設(shè)向量a和c夾角為θ
cosθ=a·c/(|a||c|=(7m/2+n/2)/[√（49/4+1/4）*1]=√2(7m/2+n/2)/5,
cosθ=b·c(/|b||c|)=(m/2+7n/2)/√[(1/4+49/4)*1]=√2(m/2+7n/2)/5,
√2(7m/2+n/2)/5=√2(m/2+7n/2)/5,
m=n,
m^2+n^2=1,
m=±√2/2,
n=±√2/2,
m,n應(yīng)取同號
則向量c=(√2/2,√2/2),c=(-√2/2,-√2/2),