Mathematics 9709 · AS & A Level · Trigonometry

Trigonometry — practice question

(i)[5]

First expand $\cos(x + 45^\circ)$, then write $\cos(x + 45^\circ) - (\sqrt{2})\sin x$ in the form $R\cos(x + \alpha)$, where $R > 0$ and $0^\circ < \alpha < 90^\circ$. State $R$ correct to 4 significant figures and $\alpha$ correct to 2 decimal places.

(ii)[4]

Hence solve the equation $\cos(x + 45^\circ) - (\sqrt{2})\sin x = 2$, for $0^\circ < x < 360^\circ$.

Worked solution & mark scheme

This 9-mark question has a full step-by-step worked solution and mark scheme. One marking point: Apply the $\cos(A+B)$ formula to rewrite the expression in terms of $\cos x$ and $\sin x$

  • Full mark scheme, point by point
  • Step-by-step worked solution
  • Write your answer & get it marked instantly by AI