JAMB - Mathematics (2025 - No. 9)
Which of the following angles cannot be constructed using a protractor, a compass, and a sharpened pencil?
135°
90°
145°
60°
Paliwanag
In classical constructions with compass and straightedge, 60° (equilateral), 90° (square), and 135° (90° + 45°) are constructible. 145° is not constructible in general (not a multiple resulting from bisections of constructible angles).