PROBLEM
6. Prove the Trig Identities.
a. cosθ×tanθ=sinθ
STEP 1
1. We assume the basic trigonometric identities are known: tanθ=cosθsinθ.
2. We assume the domain of θ is such that cosθ=0.
STEP 2
1. Express tanθ in terms of sinθ and cosθ.
2. Substitute the expression for tanθ into the left-hand side of the identity.
3. Simplify the expression to show it equals the right-hand side.
STEP 3
Start by expressing tanθ in terms of sinθ and cosθ:
tanθ=cosθsinθ
STEP 4
Substitute the expression for tanθ into the left-hand side of the identity cosθ×tanθ:
cosθ×tanθ=cosθ×cosθsinθ
SOLUTION
Simplify the expression by canceling cosθ in the numerator and the denominator:
cosθ×cosθsinθ=sinθ The identity is proven:
cosθ×tanθ=sinθ
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