Plane trigonometry, by S.L. Loney.

TRIGONOMETRICAL RATIOS.

37

Hence we observe that
the Sine of any angle = the Cosine of its complement,
the Tangent of any angle = the Cotangent of its complement,
and the Secant of an angle = the Cosecant of its complement.
From this is apparent what is the derivation of the
names Cosine, Cotangent, and Cosecant.
40. The student is advised before proceeding any
further to make himself quite familiar with the following
table. [For an extension of this table, see Art. 76.]

Angle
Sine
Cosine
Tangent
Cotangent
Cosecant
Secant

00 1 300

450

600 I 900

O 1 /3 1
1 /3 1 1 0
0.
c0 /3 1 O
/3
co 2,/2 1
1 2 __2 2 _3
-- -- s J

If the student commits accurately to memory the
portion of the above table included between the thick
lines, he should be able to easily reproduce the rest.