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Multiple Choice
Identify whether the given equation is that of a cardioid, limaçon, rose, or lemniscate. r=1−sinθ
A
Cardioid
B
Limacon
C
Rose
D
Lemniscate
Verified step by step guidance
1
Step 1: Understand the general forms of polar equations for different types of curves. A cardioid typically has the form r = a ± a sin(θ) or r = a ± a cos(θ). A limaçon has the form r = a ± b sin(θ) or r = a ± b cos(θ), where a ≠ b. A rose curve has the form r = a sin(nθ) or r = a cos(nθ), where n is an integer. A lemniscate has the form r² = a² sin(2θ) or r² = a² cos(2θ).
Step 2: Compare the given equation r = 1 - sin(θ) with the general forms. Notice that it resembles the form r = a ± a sin(θ) with a = 1.
Step 3: Recognize that when a = b in the limaçon form, the curve is specifically a cardioid. In this case, since the equation is r = 1 - sin(θ), it matches the cardioid form r = a - a sin(θ) with a = 1.
Step 4: Confirm that the equation does not fit the forms of rose curves or lemniscates, as it does not involve r² or a multiple angle like nθ.
Step 5: Conclude that the given equation r = 1 - sin(θ) is indeed a cardioid based on its form and comparison with the general equations for polar curves.