For what values of c are the vectors [-8, c, 4] and [c, c²,c] orthogonal?

Calculus: Early Transcendentals
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Chapter1: Functions And Models
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**Problem 7:** For what values of \( c \) are the vectors \([-8, c, 4]\) and \([c, c^2, c]\) orthogonal?

**Explanation:**

To determine the values of \( c \) for which the vectors are orthogonal, we need to find when their dot product is zero. The dot product of two vectors \([a_1, a_2, a_3]\) and \([b_1, b_2, b_3]\) is calculated as:

\[ a_1 \cdot b_1 + a_2 \cdot b_2 + a_3 \cdot b_3 = 0 \]

Applying this to the given vectors:

\[ (-8) \cdot c + c \cdot c^2 + 4 \cdot c = 0 \]

Simplifying:

\[ -8c + c^3 + 4c = 0 \]

\[ c^3 - 4c = 0 \]

Factor out \( c \) from the equation:

\[ c(c^2 - 4) = 0 \]

This gives:

\[ c = 0 \quad \text{or} \quad c^2 - 4 = 0 \]

Solve \( c^2 - 4 = 0 \):

\[ c^2 = 4 \]

\[ c = 2 \quad \text{or} \quad c = -2 \]

Thus, the vectors are orthogonal for \( c = 0, 2, \) or \(-2\).
Transcribed Image Text:**Problem 7:** For what values of \( c \) are the vectors \([-8, c, 4]\) and \([c, c^2, c]\) orthogonal? **Explanation:** To determine the values of \( c \) for which the vectors are orthogonal, we need to find when their dot product is zero. The dot product of two vectors \([a_1, a_2, a_3]\) and \([b_1, b_2, b_3]\) is calculated as: \[ a_1 \cdot b_1 + a_2 \cdot b_2 + a_3 \cdot b_3 = 0 \] Applying this to the given vectors: \[ (-8) \cdot c + c \cdot c^2 + 4 \cdot c = 0 \] Simplifying: \[ -8c + c^3 + 4c = 0 \] \[ c^3 - 4c = 0 \] Factor out \( c \) from the equation: \[ c(c^2 - 4) = 0 \] This gives: \[ c = 0 \quad \text{or} \quad c^2 - 4 = 0 \] Solve \( c^2 - 4 = 0 \): \[ c^2 = 4 \] \[ c = 2 \quad \text{or} \quad c = -2 \] Thus, the vectors are orthogonal for \( c = 0, 2, \) or \(-2\).
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For orthogonal,dot product of vectors is equal to zero.

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