TsAmE
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Homework Statement
Under what conditions are the following true?
a) |\mathbf{a}\cdot \mathbf{b}| =|\mathbf{a}||\mathbf{b}|
b) (\mathbf{a} + \mathbf{b}) \cdot (\mathbf{a} - \mathbf{b}) = |\mathbf{a}|^2 - |\mathbf{b}|^2
Homework Equations
None.
The Attempt at a Solution
a) I don't understand why the answer is \mathbf{a} = \lambda \mathbf{b}. Surely it would be equivalent all the time?
b) Also looks equivalent all the time to me.