(a)[3]
Determine the exact value of $x$.
(b)[3]
Hence, determine the exact sum of the first 25 terms of the progression.
Mathematics 9709 · AS & A Level · Series
Series — practice question
In an arithmetic progression, the first, third and fifth terms are $2\cos x$, $-6\sqrt{3}\sin x$ and $10\cos x$ respectively, with $\frac{1}{2}\pi < x < \pi$.
Worked solution & mark scheme
This 6-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Use the arithmetic progression terms containing $\sin x$ and $\cos x$ to write down simultaneous equations.” …
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