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AP EAMCET · Maths · Vector Algebra

Let \(\mathbf{u}\) and \(\mathbf{v}\) be two vectors in \(R^2\). If \(|\mathbf{u}+\mathbf{v}|^2=2\left(|\mathbf{u}|^2+|\mathbf{v}|^2\right)\), then .....

  1. A \(\mathbf{u}=\mathbf{v}\)
  2. B \(\mathbf{u}\) and \(\mathbf{v}\) need not be same but they have same direction
  3. C \(\mathbf{u}\) and \(\mathbf{v}\) need not be same but they have the opposite direction
  4. D \(\mathbf{u}=2 \mathbf{v}\)
Verified Solution

Answer & Solution

Correct Answer

(A) \(\mathbf{u}=\mathbf{v}\)

Step-by-step Solution

Detailed explanation

\begin{aligned} & \text { }|\mathbf{u}+\mathbf{v}|^2=2\left(|u|^2+|v|^2\right) \\ &|\mathbf{u}|^2+|\mathbf{v}|^2+2 \mathbf{u v}=2|\mathbf{u}|^2+2|\mathbf{v}|^2 \\ &|\mathbf{u}|^2+|\mathbf{v}|^2=2 \mathbf{u} \cdot \mathbf{v} \\ &|\mathbf{u}|^2+|\mathbf{v}|^2-2 \mathbf{u} \cdot…