Straight objects: lines, rays and segments

Angles and their properties.

Parallel and perpendicular lines.

Triangles: definition of a triangle, equality of two triangles by side-angle-side and by angle-side-angle.

Various types of triangles: isosceles and equilateral triangles.

Angles in a triangle, right triangles and equality of right triangles by hypotenuse-leg, equality of two arbitrary triangles by side-side-side.

Circles: definition of a circle, chords, tangent and secant lines.

Circles and angles.

Circles and triangles.

Quadrilaterals: definition of a quadrilateral, parallelograms.

Properties of parallelograms, a rectangle, a square and a rhombus.

Angles and parallel lines, triangle's midsegments.

One more type of quadrialterals: trapezoids.

Cosine of an angle, the Pythagorean theorem.

Sine and tangent of an angle, basic trigonometric formulas.

Glossary.

Test in elementary plane geometry.

Brief history of this homepage