Formula and example
How it is calculated
a·b=Σaᵢbᵢ; |a|=√(Σaᵢ²); cos(φ)=(a·b)/(|a|·|b|).
Worked example
a=(1;0;0) and b=(0;1;0) have dot product 0 and angle 90°. Their cross product is (0;0;1).
Things to check
- The angle to a zero vector is undefined. The sum, difference and dot product can still be calculated.
- For two-dimensional vectors, the signed parallelogram area is shown instead of a three-dimensional cross product.
Frequently asked questions
Why can a dot product be negative?
For two non-zero vectors, a negative dot product means their angle is greater than 90°.