)利用平面向量数量积证明不等式(x²+y²)(m²+n²)≥(xm+yn)²)利用平面向量数量积证明不等式(x²+y²)(m²+n²) ≥ (xm+yn)²(2)利用平面向量数量积证明cos(α-β)= co
来源:学生作业帮助网 编辑:作业帮 时间:2024/07/12 01:16:58
![)利用平面向量数量积证明不等式(x²+y²)(m²+n²)≥(xm+yn)²)利用平面向量数量积证明不等式(x²+y²)(m²+n²) ≥ (xm+yn)²(2)利用平面向量数量积证明cos(α-β)= co](/uploads/image/z/11533555-19-5.jpg?t=%29%E5%88%A9%E7%94%A8%E5%B9%B3%E9%9D%A2%E5%90%91%E9%87%8F%E6%95%B0%E9%87%8F%E7%A7%AF%E8%AF%81%E6%98%8E%E4%B8%8D%E7%AD%89%E5%BC%8F%EF%BC%88x%26%23178%3B%2By%26%23178%3B%29%28m%26%23178%3B%2Bn%26%23178%3B%29%E2%89%A5%28xm%2Byn%29%26%23178%3B%29%E5%88%A9%E7%94%A8%E5%B9%B3%E9%9D%A2%E5%90%91%E9%87%8F%E6%95%B0%E9%87%8F%E7%A7%AF%E8%AF%81%E6%98%8E%E4%B8%8D%E7%AD%89%E5%BC%8F%EF%BC%88x%26%23178%3B%2By%26%23178%3B%29%28m%26%23178%3B%2Bn%26%23178%3B%29+%E2%89%A5+%28xm%2Byn%29%26%23178%3B%EF%BC%882%EF%BC%89%E5%88%A9%E7%94%A8%E5%B9%B3%E9%9D%A2%E5%90%91%E9%87%8F%E6%95%B0%E9%87%8F%E7%A7%AF%E8%AF%81%E6%98%8Ecos%EF%BC%88%CE%B1-%CE%B2%EF%BC%89%3D+co)
)利用平面向量数量积证明不等式(x²+y²)(m²+n²)≥(xm+yn)²)利用平面向量数量积证明不等式(x²+y²)(m²+n²) ≥ (xm+yn)²(2)利用平面向量数量积证明cos(α-β)= co
)利用平面向量数量积证明不等式(x²+y²)(m²+n²)≥(xm+yn)²
)利用平面向量数量积证明不等式(x²+y²)(m²+n²) ≥ (xm+yn)²
(2)利用平面向量数量积证明cos(α-β)= cosαcosβ + sinαsinβ
)利用平面向量数量积证明不等式(x²+y²)(m²+n²)≥(xm+yn)²)利用平面向量数量积证明不等式(x²+y²)(m²+n²) ≥ (xm+yn)²(2)利用平面向量数量积证明cos(α-β)= co
平面向量u = (x,y)
平面向量v = (m,n)
数量积 u*v = |u||v|cos
u*v |u|^2 * |v|^2 (x²+y²)(m²+n²) ≥ (xm+yn)²
(2) u = (cos a,sin a),a = the angle between x-axis and u
v = (cos b,sin b),b = the angle between x-axis and v.
angle is the angle between u,v.==> = b - a.
数量积u*v = cos a * cos b + sin a * sin b
|u| = (cos^2 a + sin^2 a)^(1/2) = 1
|v| = 1.
u*v = |u||v| cos = cos = cos (b-a)
So,cos(b-a) = cos a cos b + sin a sin b
向量U平方是绝对值U的平方