Yes—if any angle is 90°, then all angles are right, making it a rectangle.
Key Concepts
- Criterion: Right angle implies rectangle
- Alternate: Equal diagonals imply rectangle
- Property: Opposite sides parallel
Steps
- Action: Check for a right angle
- Action: Check diagonals for equality
- Action: Conclude rectangle if condition holds
Formula
$$mathbf{a} cdot mathbf{b} = 0 quad text{(adjacent sides perpendicular)}$$
$$|mathbf{a} + mathbf{b}| = |mathbf{a} – mathbf{b}| quad text{(diagonals equal)}$$