Angle is not Invariant under Affine Transformation

Theorem

The angle between two (straight) lines does not necessarily stay the same under an affine transformation.

Proof

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Sources

• 1998: David Nelson: The Penguin Dictionary of Mathematics (2nd ed.) ... (previous) ... (next): affine transformation
• 2008: David Nelson: The Penguin Dictionary of Mathematics (4th ed.) ... (previous) ... (next): affine transformation