Geometry Key terms and concepts by Mr. Gibbon

Scale Drawing

jewellgibbons — 2025-02-10 20:50:44 UTC

Scale Drawing that shows a real object with accurate sizes reduced or enlarged by a certain amount (called the scale).

The scale is shown as the length in the drawing, then a colon (":"), then the matching length on the real thing.

Sine

jewellgibbons — 2025-03-16 21:24:52 UTC

For right triangles ONLY, this is the ratio of the opposite side divided by the hypotenuse.

Scale Factor

jewellgibbons — 2025-03-16 21:25:21 UTC

The value multiplied by the pre-image (old image) side lengths to get the image (new image) side lengths.

Proportion

jewellgibbons — 2025-03-16 21:25:33 UTC

A proportion is two fractions that are equal to each other. Similar figures generate multiple proportions as all corresponding side lengths are related by the same scale factor.

Similar Triangles

jewellgibbons — 2025-03-16 21:25:42 UTC

Triangles that are related by a dilation. Corresponding side lengths are proportional and corresponding angles are congruent.

Angle-Angle Similarity

jewellgibbons — 2025-03-16 21:25:51 UTC

Given two triangles, if we know that two angles are congruent, we know the triangles are similar.

Cosine

jewellgibbons — 2025-03-16 21:26:22 UTC

For right triangles ONLY, this is the ratio of the adjacent side divided by the hypotenuse.

Tangent

jewellgibbons — 2025-03-16 21:26:54 UTC

For right triangles ONLY, this is the ratio of the opposite side divided by the adjacent side.

Adjacent Side

jewellgibbons — 2025-03-16 21:27:04 UTC

The side length touching the reference angle that is not the hypotenuse.

Opposite side

jewellgibbons — 2025-03-16 21:27:31 UTC

The side across (opposite) to the reference angle.

Hypotenuse

jewellgibbons — 2025-03-16 21:27:43 UTC

The longest side length of a right triangle found directly across from the right angle.

Pythagorean Theorem

jewellgibbons — 2025-03-16 21:27:54 UTC

a^2+b^2=c^2 for any right triangle

LT1 - Copy an angle

jewellgibbons — 2025-09-08 22:53:05 UTC

LT2 - Bisect an angle

jewellgibbons — 2025-09-08 22:53:13 UTC

LT 3 - Perpendicular bisector

jewellgibbons — 2025-09-08 22:53:22 UTC

LT 4 - Perpendicular line through a point

jewellgibbons — 2025-09-08 22:53:32 UTC

Parallel through a point

jewellgibbons — 2025-09-08 22:53:41 UTC

Inscribed

jewellgibbons — 2025-09-10 18:12:15 UTC

When a figure is inscribed, it is completely inside another figure so that their sides, edges, vertices, or curves touch.

A polygon is inscribed in a circle if it fits inside the circle and every vertex of the polygon is on the circle.
A circle is inscribed in a polygon if it fits inside the polygon and every side of the polygon is tangent to the circle.

Circle

jewellgibbons — 2025-09-10 18:23:17 UTC

A circle of radius r with center O is the set of all points that are a distance r units from O.

To draw a circle of radius 3 units and center O, use a compass to draw all the points at a distance 3 units from O.

line segment

jewellgibbons — 2025-09-10 18:23:39 UTC

A line segment is the set of all points on a line between two endpoints.

Parallel

jewellgibbons — 2025-09-10 18:24:53 UTC

Two lines that never intersect are called parallel. Line segments can also be parallel if they extend into parallel lines.

This figure shows two parallel line segments.

Conjecture

jewellgibbons — 2025-09-10 18:26:50 UTC

A conjecture is a reasonable guess that someone is trying to either prove or disprove.

Perpendicular bisector

jewellgibbons — 2025-09-10 18:27:15 UTC

The perpendicular bisector of a segment is a line through the midpoint of the segment that is perpendicular to the segment.

In this diagram, the dashed line is the perpendicular bisector of segment .

Translate

jewellgibbons — 2025-12-15 20:18:07 UTC

Translate OBJECT by Directed Line Segment from _________ to _____________.

Rotate

jewellgibbons — 2025-12-15 20:18:34 UTC

Rotate OBJECT _______ degrees with center _______.

Reflect

jewellgibbons — 2025-12-15 20:18:56 UTC

Reflect OBJECT over line ___________.

Angle - Side - Angle Triangle congruence

jewellgibbons — 2025-12-15 20:21:18 UTC

Side - Angle - Side Triangle Congruence

jewellgibbons — 2025-12-15 20:22:19 UTC

Side - Side - Side Triangle congruence

jewellgibbons — 2025-12-15 20:22:33 UTC