It's not that hard. See link above. In particular "low tetra" set and several others on list.

OMG! Oh Heck!!!! This is partly why his instructions are somewhat hard to follow.

Quote from site:
Trigonometry is a branch of Mathematics that deals with Triangles.� At the heart of Trigonometry, are angles.



We measure Angles in degrees (�).� Each degree subdivides into 60 minutes (') or 1/60th of a degree, and each minute subdivides again into 60 seconds (") or 1/60th of a minute.� To use the Degree mark (�) on most computer keyboards, hold down the �Alt' key and press 0176 on the numeric keypad (Alt + 0176).



There are 360� in a Circle, and 180� in a Straight Line.� A Right Angle is 90� (exactly), and a small square is its symbol, unlike the arcs used for other angles.� An Acute (sharp) Angle is between 0� and 90�.� An Obtuse (blunt) Angle is between 90� and 180�.� A Reflex (bent back) Angle is between 180� and 360�.�



The sum of the internal angles in a Triangle is 180� (half that of a Circle).� An Equilateral Triangle has ALL sides equal in length, and ALL angles equal to 60�.� An Isosceles Triangle has TWO sides equal in length, with TWO angles equal to each other.� A Scalene Triangle has NO sides or angles equal to any other.



A Right-Angled Triangle has a Right Angle (90�) inside it.� The Hypotenuse is a special name used for the side of a triangle opposite a Right Angle (note that an �opposite' side does NOT touch the angle in question).� The Hypotenuse is ALWAYS the longest side in a triangle.