Dot products

The dot products between two unitized objects of the same type are listed in the following table. The vector $$\mathbf v$$ is the difference between their center positions, and the scalars $$r_1$$ and $$r_2$$ are their radii. In the case of dipoles and circles, the vectors $$\mathbf n_1$$ and $$\mathbf n_2$$ correspond to the directions of the carrier lines or the normals of the carrier planes.

Type	Dot Product
Round points $$\mathbf a_1$$ and $$\mathbf a_2$$	$$\mathbf a_1 \mathbin{\unicode["segoe ui symbol"]{x2022}} \mathbf a_2 = -\dfrac{1}{2}(\mathbf v^2 + r_1^2 + r_2^2)$$
Dipoles $$\mathbf d_1$$ and $$\mathbf d_2$$	$$\mathbf d_1 \mathbin{\unicode["segoe ui symbol"]{x2022}} \mathbf d_2 = -\dfrac{1}{2}(\mathbf n_1 \cdot \mathbf n_2)(\mathbf v^2 + r_1^2 + r_2^2) + (\mathbf n_1 \cdot \mathbf v)(\mathbf n_2 \cdot \mathbf v)$$
Circles $$\mathbf c_1$$ and $$\mathbf c_2$$	$$\mathbf c_1 \mathbin{\unicode["segoe ui symbol"]{x2022}} \mathbf c_2 = +\dfrac{1}{2}(\mathbf n_1 \cdot \mathbf n_2)(\mathbf v^2 - r_1^2 - r_2^2) - (\mathbf n_1 \cdot \mathbf v)(\mathbf n_2 \cdot \mathbf v)$$
Spheres $$\mathbf s_1$$ and $$\mathbf s_2$$	$$\mathbf s_1 \mathbin{\unicode["segoe ui symbol"]{x2022}} \mathbf s_2 = +\dfrac{1}{2}(\mathbf v^2 - r_1^2 - r_2^2)$$

See Also

• Geometric products
• Exterior products