Page 26 - Ebook Trigonometri_Krisna Hasugian_MESP 2019

USING DEFINITIONS AND FUNDAMENTAL IDENTITIES OF TRIG
FUNCTIONS

Fundamental Identities

Reciprocal Identities

sin = 1/(csc ) csc = 1/(sin )

cos = 1/(sec ) sec = 1/(cos )

tan = 1/(cot ) cot = 1/(tan )

Quotient Identities

tan = (sin )/(cos ) cot = (cos )/(sin )

Pythagorean Identities

sin² + cos² = 1

1+ tan² = sec²

1+ cot² = csc²

Negative Angle Identities

sin(− ) = − sin cos(− ) = cos tan(− ) = − tan

csc(− ) = − csc sec(− ) = sec cot(− ) = − cot

Complementary Angle Theorem

If two acute angles add up to be 90°, they are considered complimentary.

The following are considered cofunctions:

sine and cosine tangent and cotangent secant and cosecant

The complementary angle theorem says that cofunctions of complimentary

angles are equal.

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