2025 PHS P1 Q10

2025 PHS P1 Q10

Secondary 4
5 marks

Do not use a calculator in this question.

  1. Find the exact value of \(\cos85^\circ\cos40^\circ+\sin85^\circ\sin40^\circ\).[2]
  2. Show that \(\sin\dfrac{5\pi}{12}=\dfrac{\sqrt6+\sqrt2}4\).[3]

Solution:

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Answer:(a) \(\dfrac{\sqrt2}2\). (b) \(\dfrac{\sqrt6+\sqrt2}4\) (shown).

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