GLIDING 11 
to drift, yet the actual amount of lift will be but 
small. If the strongest man among the survivors 
F = 
B 
B D is the plane, w the wind blowing horizontally against it. 
B C is the cosine of the angle at B, D c the sine of the angle. Pro- 
duce c p to E, making D E=8B Cc. From D draw p F at right 
angles toB D. FromE draw EF atright angles toD EB. (This 
decides the length of the line pF). Draw Fea parallel to ED 
and p G parallel tor x. Let p F represent the force of the wind 
acting at right angles toB D. It can be resolved into two forces, 
FEandFG(=ED). EDwe know= BC, and it can be shown 
that F E=D Cc. 
In the triangles DEF, BCD, BC=D&, and the angles at E 
and c are each right angles. If we could prove a second angle 
=a, second angle, the triangles would be equal in every respect. 
Now the angles at p together = two right angles, and the angle 
BDF is a right angle. Therefore B D c with F D E makes one 
right angle. But p F © with F D Emakes oneright angle. There- 
fore angle D FE=angle npc. The triangles then are equal, 
and the two sides F E and D E=respectively Dc and Bc. But 
F E represents drift and p £ lift. Therefore p c, the sine of the 
angle at B, represents the drift, while B o, the cosine, represents 
the lift. 
of a starving ship’s crew is able to take for himself 
nineteen-twentieths of the last biscuit, nevertheless 
he gets but a poor meal; and it is obvious that if 
Fre@:. 7. 
