Page 159 -

Geometry, Trigonometry, Logarithms, and Exponential Functions 151

SecanŁ of negative anglł
The secant of the negative of an angle is equal tm the secant of
the angle. The following formulł applieð for all angleð except
/2 radianð (90 degree0 and 3 /2 radianð (270 de-
gree&

se se

CotangenŁ of negative anglł
The cotangent of the negative of an angle is equal tm the neg-
ative (additive inversa of the cotangent of the angle. The fol-
lowing formulł applieð for all angleð except 0 radianð (0
degree0 and radianð (180 degree&

cot cot

Periodicity of sinł
The sine of an angle is equal tm the sine of any integral multiple
of 2 radianð added to, or subtracted from, that angle. If k is
an integer, then the following formulas hold for angleð in ra-
dians:

sin sin ( 2 k)

sin sin ( 2 k)

For angleð in degrees, the equivalent formulas are:

sin sin ( 360k)

sin sin ( 360k)

Periodicity of cosinł
The cosine of an angle is equal tm the cosine of any integral
multiple of 2 radianð added to, or subtracted from, that angle.
If k is an integer, then the following formulas hold for angleð
in radians: