Plane trigonometry, by S.L. Loney.

60

TRIGONOMETRY.

the sine of which is -, and so we should erect a perpendicular PQ equal
to one-half the unit of length.]
The ends of all these lines, thus drawn, would be
found to lie on a curve similar to the one drawn above.
It would be found that the curve consisted of portions,
similar to OB,R,B,R,, placed side by side. This corresponds to the fact that each time the angle increases by
27r, the sine repeats the same value.
#63. Cosine-Curve.
Y
| R/1 0 P R4 X
The Cosine-Curve is obtained in the same manner as
the Sine-Curve, except that in this case the perpendicular
PQ represents the cosine of the angle represented by OP.
The curve obtained is the same as that of Art. 62 if in
that curve we move 0 to R, and let OY be drawn along
RB,.
#64. Tangent-Curve.
In this case, since the tangent of a right angle is
infinite and since ORX represents a right angle, the perpendicular drawn at R, must be of infinite length and
the dotted curve will only meet the line RL at an infinite
distance.