OCR H240/03 — Question 8

Exam BoardOCR
ModuleH240/03 (Pure Mathematics and Mechanics)
TopicSine and Cosine Rules

8 In this question you must show detailed reasoning. The diagram shows triangle \(A B C\).
\includegraphics[max width=\textwidth, alt={}, center]{ec83c2c5-f8f8-4357-abfa-d40bc1d026b4-06_737_1383_456_342} The angles \(C A B\) and \(A B C\) are each \(45 ^ { \circ }\), and angle \(A C B = 90 ^ { \circ }\).
The points \(D\) and \(E\) lie on \(A C\) and \(A B\) respectively. \(A E = D E = 1 , D B = 2\). Angle \(B E D = 90 ^ { \circ }\), angle \(E B D = 30 ^ { \circ }\) and angle \(D B C = 15 ^ { \circ }\).
  1. Show that \(B C = \frac { \sqrt { 2 } + \sqrt { 6 } } { 2 }\).
  2. By considering triangle \(B C D\), show that \(\sin 15 ^ { \circ } = \frac { \sqrt { 6 } - \sqrt { 2 } } { 4 }\).