| Exam Board | Edexcel |
|---|---|
| Module | C2 (Core Mathematics 2) |
| Marks | 5 |
| Paper | Download PDF ↗ |
| Topic | Sine and Cosine Rules |
| Type | Triangle with trigonometric identities |
| Difficulty | Moderate -0.8 This is a straightforward application of the cosine rule followed by using the Pythagorean identity. Part (a) requires direct substitution into the cosine rule formula (a standard C2 technique), and part (b) is routine use of sin²A + cos²A = 1. Both parts are mechanical with no problem-solving or insight required, making this easier than average. |
| Spec | 1.05b Sine and cosine rules: including ambiguous case1.05j Trigonometric identities: tan=sin/cos and sin^2+cos^2=1 |
\includegraphics{figure_1}
Figure 1 shows the triangle $ABC$, with $AB = 6$ cm, $BC = 4$ cm and $CA = 5$ cm.
\begin{enumerate}[label=(\alph*)]
\item Show that $\cos A = \frac{3}{4}$.
[3]
\item Hence, or otherwise, find the exact value of $\sin A$.
[2]
\end{enumerate}
\hfill \mbox{\textit{Edexcel C2 Q4 [5]}}