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Originally Posted by

**Joker** [1. Use a Sum or difference identity to find the exact value of sin285degrees

Expand that using the 'sum or difference' formula for sine.

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2. If tanX = -3/4 and 90<x<180, find cosX (the 90 and 180 are degrees)

Pythagoras' theorem: If , then ...

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3. If (tanX)(cscX) = 3, find value of cosX

so

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4. If tanX= 3/4 and 180<X<270, find the exact value of sin2X

Write in terms of and and use the identity .

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5. Find the value of tan(A+b) if cosA = 13/5, tanB = 3/4, and 0<A<90

Write , use the 'sum-difference' formulas on both the

numerator and the denominator, and write in terms of sine and cosine.