Question

Students were asked to simplify the expression the quantity cosecant theta minus sine theta end quantity over cosecant period Two students' work is given. (In image below)
Part A: Which student simplified the expression incorrectly? Explain the errors that were made or the formulas that were misused. (5 points)


Part B: Complete the student's solution correctly, beginning with the location of the error. (5 points)

Answer 1

Answer:

  A.  student A is correct; student B was confused by the division

  B.  3: cos²(θ)/(sin(θ)csc(θ)); 4: cos²(θ)

Step-by-step explanation:

Each student correctly made use of the trig identities ...

  csc(θ) = 1/sin(θ)

  1 -sin²(θ) = cos²(θ)

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A.

Student A's work is correct.

Student B apparently got confused by the two denominators in Step 2, and incorrectly replaced them with their quotient instead of their product.

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B.

The transition from Step 2 can look like ...

  $\textsf{Step 3: }\ \dfrac{\left(\dfrac{1-\sin^2\theta}{\sin\theta}\right)}{\csc\theta}=\dfrac{1-\sin^2\theta}{\sin\theta}\cdot\dfrac{1}{\csc\theta}=\dfrac{\cos^2\theta}{(\sin\theta)(\csc\theta)}\\\\\textsf{Step 4: }\ \cos^2\theta$