GATE CSE 2021 Set 1 Q2: Which shape is not a convex polygon

A polygon is convex if, for every pair of points, P and Q belonging to the polygon, the line segment PQ lies completely inside or on the polygon.

Which one of the following is NOT a convex polygon?

Try it: multiple choice: exactly one correct option

Wrong answer costs 1/3 mark in GATE.

Show answer and explanation

Answer: A (official GATE 2021 final answer key)

Concept used: A polygon is convex exactly when every interior angle is less than $180^\circ$ (no dents).

First step: Look for a shape with an inward notch: a segment joining two points on either side of the notch leaves the shape.

Full step-by-step solution

Detailed working, common mistakes and linked mock tests will be available with a free GATEiit account. Log-in is coming soon.

Share this question

Source: official GATE 2021 Set 1 CS question paper and final answer key, organised by IIT Bombay. Question paper · Answer key