平面向量夹角的坐标公式

---

---

---

cos\langle \vec{a},\vec{b}\rangle =\frac {{x}_{1}{x}_{2}+{y}_{1}{y}_{2}} {\sqrt {{{x}_{1}}^{2}+{{x}_{2}}^{2}}\sqrt {{{y}_{1}}^{2}+{{y}_{2}}^{2}}}

---