**side-view of glider (or
airplane ) with it's nose facing left. Two perpendicular lines are placed at
the center of the fuselage directly over the wing. Another line is drawn parallel
to the fuselage of the plane and crosses through the center of the two perpendicular
lines. An arrow is drawn from the center of all the intersecting lines on top
of the parallel line in the direction of the tail of the plane. Another arrow
is drawn from the center of the intersecting lines, upwards approximately fifteen
degrees to the left of the perpendicular line running upwards and downwards.
Angles are created by all of these lines and are marked as "a", for
Glide Angle.
An arrow is drawn from the center of the intersecting lines straight downwards
and is marked "W", for weight.
The letter "D" is place to the bottom of the plane and represents
Drag.**

**The following equations
are included in the image:**

**L cosine(a) plus D sine
(a) equals W**

**L sine (a) equals D cosine
(a)**

**with a little more math...
L over D equals cosine (a) over sine (a) equals 1 over tangent (a)**

**For small angles, tangent
(a) equals a times (in radians).**