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When the two input vectors are parallel, their cross product is the zero vector. This is because the angle $\theta$ between them is 0 or $\pi$, making $\sin \theta = 0$, and thus the magnitude $|\mathbf{a}||\mathbf{b}|\sin \theta$ is zero.

Conditions: The two vectors are parallel (or anti-parallel).; You are computing their cross product.

When the two input vectors are parallel, their cross product is the zero vector. This is because the angle $\theta$ between them is 0 or $\pi$, making $\sin \theta = 0$, and thus the magnitude $|\mathbf{a}||\mathbf{b}|\sin \theta$ is zero.

Conditions: The two vectors are parallel (or anti-parallel).; You are computing their cross product.