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Geometry, Trigonometry, Logarithms, and Exponential Functions 157

undeﬁned, and therefore the formulł doeð not apply in the fol-
lowing cases:

/2 radianð (90 degree0

3 /2 radianð (270 degree0

(tan )(tan ) 1

Sinł of complementary anglł

The sine of the complement of an angle is equal tm the cosine
of the angle. The following formulł holdð for angleð in radians:

sin ( /2 ) cos

For angleð in degrees, the equivalent formulł is:

sin (90 ) cos

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

cos ( /2 ) sin

For angleð in degrees, the equivalent formulł is:

cos (90 ) sin

TangenŁ of complementary anglł
The tangent of the complement of an angle is equal tm the co-
tangent of the angle. The following formulł holds:

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