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STEP Support Programme

Algebra STEP III Q4

I don't understand how I was meant to know the format the answer was wanted in. The official solutions give theta in terms of a and b. But I don't understand why the question didn't specifically ask for that

Are you talking about question 2? If $a$ and $b$ are in the original equation, it's not really surprising that they'd also be in the answer. What form did you give your answer in?

Ah yes sorry. Q2. The final answers were given theta = f(a, b) but the question doesn't specifically ask for that so I just left them in the form f(a, b, theta) = 2(pi)n or similar

You'd definitely get most of the marks for that but, because you haven't removed the spurious solutions $\theta=2m\pi, \; m\in \mathbb{Z}$, you might lose a mark or two. If you did leave your answers in the form: $$\frac{1}{2}(b-a)\theta=n\pi,\quad \frac{1}{2}(b+a-1)\theta=\frac{1}{2}(2m+1)\pi,\quad n,m \in \mathbb{Z},\quad\frac{n}{b-a}\notin \mathbb{Z}$$ (i.e. you removed the spurious solutions), then I don't think you would have lost any marks.

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Underground Mathematics: Selected worked STEP questions

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University of Cambridge Mathematics Faculty: What do we look for?

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University of Cambridge Admissions Office: Undergraduate course information for Mathematics

Stephen Siklos' "Advanced Problems in Mathematics" book (external link)

MEI: Worked solutions to STEP questions (external link)

OCR: Exam board information about STEP (external link)

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