1. TRIGONOMETRIC IDENTITIES
Reciprocal Identities
Tangent & Cotangent Identities
Pythagorean Identities

2. Cofunction Identities
( is the complement of )
Negative Identity Functions

3. Ex. Solve for values between 0˚ & 90˚
1. If tan Ø=2, find cot Ø.
2. If tan Ø=7/2 , find sin Ø.
Recall: tan = O/A r 7 2
Use Pythagorean Theorem to find r (hypotenuse):

4. Ex. Express each value as a function of
an angle in Quadrant I.
1. sin 458˚
sin 458˚= sin 82˚
458˚=360˚+98˚
98˚ is an 82˚ in Quad. II
98˚
458˚
82˚
Back in the day before there was a plethera of calculators,
books had trig tables that listed the sin, cos, & tan for angles
between 0˚ & 90˚ (in Quad. I)…these were ‘reference angles’
for the rest of the angles. Therefore, 82˚ is a reference angle.

5. Ex. Simplify. 1.
Recall:

6. Ex. Simplify. 2. Recall: (…find LCD which is cos x)
(…since sin2x + cos2x=1)
(…since sec x is reciprocal of cos x)