Example image of eyePlorer eyePlorer map for 'Constructible number': Compass and straightedge constructions Coordinate system Euclidean geometry Length Line segment Point (geometry) Complex number If and only if Real number Imaginary part Real part Characterization (mathematics) Complex conjugate Field extension Rational number Square root Abstract algebra Line-line intersection Permutation Algebraic number Ancient Greece Counterexample Cut-the-Knot Philo line Doubling the cube Exact trigonometric constants Heptagon Angle trisection Squaring the circle Algebra Proof of impossibility Semitone History of elementary algebra