Mathematics Grade 12 15 min

Linear combinations of threedimensional vectors

Linear combinations of threedimensional vectors

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Introduction & Learning Objectives

Learning Objectives Define a linear combination of three-dimensional vectors. Express a given vector as a linear combination of other vectors by setting up and solving a system of linear equations. Determine if a vector lies in the span of a given set of vectors. Define linear dependence and independence in the context of three-dimensional vectors. Relate the concept of linear dependence of three vectors to the geometric property of being coplanar. Solve problems involving linear combinations in both algebraic and geometric contexts. šŸš€ Imagine you're piloting a spacecraft. Can you reach any point in the universe by only moving along three pre-set directional paths? This tutorial explores linear combinations, the mathematical method for 'mixing' vectors to cr...
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Key Concepts & Vocabulary

TermDefinitionExample Vector (in ā„Ā³)A quantity having both magnitude and direction in three-dimensional space, typically represented by a directed line segment or in component form as \vec{v} = <x, y, z>.The vector \vec{u} = <3, 4, 5> represents a displacement of 3 units along the x-axis, 4 units along the y-axis, and 5 units along the z-axis. ScalarA real number that is used to scale a vector. Multiplying a vector by a scalar changes its magnitude and may reverse its direction if the scalar is negative.If \vec{v} = <1, 2, 3>, then 5\vec{v} = <5, 10, 15> is a vector in the same direction but five times the magnitude. Linear CombinationA vector that is the sum of scalar multiples of two or more other vectors.Given \vec{u} = <1, 0, 0> and \vec{v} = <0, 1, 0&...
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Core Formulas

Linear Combination Equation A vector \vec{p} is a linear combination of vectors \vec{v_1}, \vec{v_2}, and \vec{v_3} if there exist scalars c_1, c_2, and c_3 such that: \vec{p} = c_1\vec{v_1} + c_2\vec{v_2} + c_3\vec{v_3} This is the fundamental equation used to set up problems. The goal is typically to find the scalars c_1, c_2, and c_3 or to determine if they exist. System of Linear Equations Given \vec{p}=<p_x, p_y, p_z> and \vec{v_n}=<x_n, y_n, z_n>, the vector equation expands into a system of linear equations: c_1x_1 + c_2x_2 + c_3x_3 = p_x c_1y_1 + c_2y_2 + c_3y_3 = p_y c_1z_1 + c_2z_2 + c_3z_3 = p_z This system is formed by equating the corresponding components (x, y, and z) of the vector equation. Solving this system for c_1, c_2, and c_3 is the pri...

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Sample Practice Questions

Easy
Which of the following best defines a linear combination of three-dimensional vectors?
A.The dot product of the vectors, resulting in a scalar.
B.vector formed by the sum of scalar multiples of other vectors.
C.The cross product of the vectors, resulting in an orthogonal vector.
D.set of vectors that all have the same magnitude.
Easy
In the context of three-dimensional vectors, what is the geometric meaning of a set of three vectors being linearly dependent?
A.They are coplanar (they all lie on the same plane).
B.They are mutually orthogonal (perpendicular to each other).
C.They are all unit vectors.
D.They must all be parallel to each other (collinear).
Easy
Which equation correctly represents the vector `p` as a linear combination of vectors `v₁`, `vā‚‚`, and `vā‚ƒ` with scalars `c₁`, `cā‚‚`, and `cā‚ƒ`?
A.p = c₁v₁ + cā‚‚vā‚‚ + cā‚ƒvā‚ƒ
B.p = (c₁+cā‚‚+cā‚ƒ)(v₁+vā‚‚+vā‚ƒ)
C.p = c₁(v₁ ā‹… vā‚‚) + cā‚ƒvā‚ƒ
D.p = c₁(v₁ Ɨ vā‚‚) + cā‚ƒvā‚ƒ

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