Illustration of a right circular cone resting on an element such that the vertex is on the bottom and…

Circles should be unshaded or shaded evenly with thick and thin lines, changing at about 45 degrees.

Triangles are used in drawing lines at right angles to the T-square.

Illustration of perpendicular lines. Intersecting lines that meet at a right angle.

Illustration of perpendicular lines with the horizontal and vertical lines labeled. "A horizontal line…

Triangles are made of various substances such as wood, rubber, celluloid, and steel.

Triangles are made of various substances such as wood, rubber, celluloid, and steel.

Illustration of the resultant vector when two vectors are acting upon a body at point P at 90 degrees.