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Lesson 5.1 Fundamental Trig Identities
An identity is an equation that is always true
throughout its domain.
Reciprocal Identities:
Quotient Identities:
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Pythagorean Identities:
• (x, y)
θ
(1, 0)
•
Verify the first Pythagorean identity using the unit circle
definitions of the sine and cosine. Then rewrite it two
additional ways.
Find sin θ and cos θ if tan θ = and sin θ > 0.
Use the Pythagorean identities not reference
triangles.
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Cofunction Identities:
Cofunctions of complementary angles are equal.
Odd-even Identities:
Even
Odd
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Example 1
Example 2
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Example 3
Example 4
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Example 5
Example 6 Page 452 #52.
Solve the equation
on the interval
Then find all real
solutions.
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