Cross Product Calculator
Free Cross product Calculator for coordinate geometry. Enter values to get step-by-step solutions with formulas and graphs.
Formula
A x B = (a2b3 - a3b2, a3b1 - a1b3, a1b2 - a2b1)
The cross product is computed using the determinant of a 3x3 matrix with unit vectors i, j, k in the first row and the components of vectors A and B in the second and third rows. The result is perpendicular to both input vectors.
Worked Examples
Example 1: Cross Product of Two 3D Vectors
Problem: Find the cross product of A = (2, 3, 4) and B = (5, 6, 7).
Solution: A x B = (a2*b3 - a3*b2, a3*b1 - a1*b3, a1*b2 - a2*b1)\n= (3*7 - 4*6, 4*5 - 2*7, 2*6 - 3*5)\n= (21 - 24, 20 - 14, 12 - 15)\n= (-3, 6, -3)\n|A x B| = sqrt(9 + 36 + 9) = sqrt(54) = 7.3485\nParallelogram area = 7.3485 sq units
Result: Cross Product: (-3, 6, -3) | Magnitude: 7.3485 | Triangle Area: 3.6742
Example 2: Perpendicular Vectors Cross Product
Problem: Find A x B where A = (1, 0, 0) and B = (0, 1, 0).
Solution: A x B = (0*0 - 0*1, 0*0 - 1*0, 1*1 - 0*0)\n= (0, 0, 1)\n|A x B| = 1\nAngle = 90 degrees (perpendicular vectors)\nThe result (0, 0, 1) = k-hat, the unit z-vector
Result: Cross Product: (0, 0, 1) | Magnitude: 1 | Angle: 90 degrees
Frequently Asked Questions
What is the cross product of two vectors?
The cross product (also called the vector product) is a binary operation on two vectors in three-dimensional space that produces a third vector perpendicular to both input vectors. Unlike the dot product which yields a scalar, the cross product yields a vector. The direction of the resulting vector follows the right-hand rule: if you curl the fingers of your right hand from vector A toward vector B, your thumb points in the direction of A cross B. The magnitude of the cross product equals the area of the parallelogram formed by the two vectors. The cross product is only defined for 3D vectors (and 7D, but that is rarely used).
How is the cross product calculated using the determinant formula?
The cross product A x B is calculated using a 3x3 determinant with the unit vectors i, j, k in the first row. For A = (a1, a2, a3) and B = (b1, b2, b3), the formula expands to: i(a2*b3 - a3*b2) - j(a1*b3 - a3*b1) + k(a1*b2 - a2*b1). This can be remembered by covering each column of the unit vectors and computing the 2x2 determinant of the remaining elements, alternating signs. The resulting vector (a2*b3 - a3*b2, a3*b1 - a1*b3, a1*b2 - a2*b1) is guaranteed to be perpendicular to both A and B, which can be verified by computing the dot product with each input vector.
What is the geometric meaning of the cross product magnitude?
The magnitude of the cross product |A x B| equals |A| * |B| * sin(theta), where theta is the angle between vectors A and B. Geometrically, this value represents the area of the parallelogram formed by the two vectors when placed tail-to-tail. Half of this magnitude gives the area of the triangle formed by the two vectors. When the vectors are parallel (theta = 0 or 180 degrees), the cross product magnitude is zero because the parallelogram degenerates into a line segment with no area. When the vectors are perpendicular (theta = 90 degrees), the magnitude is maximized at |A| * |B|. This area interpretation is widely used in physics and computer graphics.
What is the right-hand rule and how does it determine cross product direction?
The right-hand rule is a convention used to determine the direction of the cross product vector. To apply it, point the fingers of your right hand in the direction of the first vector A, then curl them toward the second vector B through the smaller angle between them. Your thumb will point in the direction of A x B. This means that the cross product is anti-commutative: A x B = -(B x A), so reversing the order reverses the direction. The right-hand rule is fundamental in physics for determining the direction of magnetic forces, torques, and angular momentum vectors. It establishes a consistent convention for defining positive rotation direction.
When is the cross product zero and what does it mean?
The cross product of two vectors is the zero vector when the input vectors are parallel or anti-parallel (pointing in the same or opposite directions). This occurs because the sine of 0 degrees and 180 degrees is zero, making |A x B| = |A|*|B|*sin(theta) = 0. The cross product is also zero if either input vector is the zero vector. Geometrically, parallel vectors cannot form a parallelogram with any area, so the cross product has zero magnitude. This property is commonly used as a test for parallelism: if A x B equals the zero vector, then A and B are parallel (or one is zero). In computational geometry, this test helps determine if line segments are collinear.
How is the cross product used in physics and engineering?
The cross product has extensive applications in physics and engineering. In electromagnetism, the magnetic force on a charged particle is F = qv x B (charge times velocity cross magnetic field). Torque is calculated as tau = r x F (position vector cross force). Angular momentum is L = r x p (position cross momentum). In fluid dynamics, the curl of a velocity field uses cross products to measure rotation. In structural engineering, moments about a point are computed using cross products. In computer graphics, cross products determine surface normals for lighting calculations and are used in ray-triangle intersection tests for 3D rendering algorithms.