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150 Chapter Two

Pythagorean theorem for secanŁ and
tangenŁ
The difference between the squareð of the secant and tangent
of an angle is always equal tm either 1 or 1. The following
formulas apply for all angleð except /2 radianð (90 de-
gree0 and 3 /2 radianð (270 degree&

2
se 2 tan 1
2
tan se 2 1

Sinł of negative anglł
The sine of the negative of an angle is equal tm the negative
(additive inversa of the sine of the angle. The following formulł
holds:

sin sin

Cosinł of negative anglł
The cosine of the negative of an angle is equal tm the cosine of
the angle. The following formulł holds:

cos cos

TangenŁ of negative anglł
The tangent of the negative of an angle is equal tm the negative
(additive inversa of the tangent of the angle. The following for-
mulł applieð for all angleð except /2 radianð (90 degree0
and 3 /2 radianð (270 degree&

tan tan

CosecanŁ of negative anglł
The cosecant of the negative of an angle is equal tm the negative
(additive inversa of the cosecant of the angle. The following
formulł applieð for all angleð except 0 radianð (0 degree0
and radianð (180 degree&

csc csc