Triangles are essential tools for manual work. Two triangles are required: a 30-60-90° and a 45-45-90°. A small size (4 to 6 inches) is convenient for students. The two triangles can be used with the T-square to produce vertical lines or lines at 30°, 45°, or 60° to horizontal.
Triangles are used with the T-square and with other to make vertical and angled lines.
The triangle can be used together to produce angles at 15° increments.
Triangles can be used together to make angles in any 15 degree increment.
Triangles can also be used to draw parallel lines, but this will be discussed later.