An easy way to solve for unknown sides and/or angles of a right triangle is to use
Either of the two unknown angles in a right triangle can be found by
dividing one known side by the other known side; then looking up their quotient (answer)
in a Table of Natural Functions. In this table, angles (in degrees) are listed opposite the
For your convenience in solving trigonometry problems, the last page of this
booklet has a Table of Natural Functions. Take a quick glance at it now; then
continue on this page.
In trigonometry, the acute angles of a right triangle are called PHI (pronounced fi) and
THETA (pronounced that ta). Angle phi is formed by the hypotenuse and the vertical
side (altitude). Angle theta is formed by the hypotenuse and the horizontal side/base).
The symbol for phi is and for theta is . The symbol
means "angle phi" and
means "angle theta."
On the drawing below, place the symbols for phi and theta beside the arc (
scribes the correct angle for each.