(a)[3]
Find the value of $\theta$. Round your answer to 3 significant figures.
(b)[2]
Find the exact value for the sum to infinity.
Mathematics 9709 · AS & A Level · Series
Series — practice question
A geometric progression starts with first term $a$ and has common ratio $\cos\theta$, where $0 < \theta < \frac{1}{2}\pi$. The second term is given as $8$ and the fifth term as $\frac{1}{8}$.
Worked solution & mark scheme
This 5-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Indicate or show that the second and fifth terms are $a\cos\theta$ and $a\cos^4\theta$ or that $r^3=\frac1{64}$” …
- Full mark scheme, point by point
- Step-by-step worked solution
- Write your answer & get it marked instantly by AI