2025 SCGS PRELIMS P1 Q9
2025 SCGS PRELIMS P1 Q9
Secondary 4
8 marks
- Show that the value of \(\sin105^\circ\) can be expressed as \(\frac{1}{4}(p+q)\), where \(p\) and \(q\) are constants.[3]
- Given that \(\frac{\cos(A+B)}{\cos(A-B)}=\frac{2}{7}\) and \(\sin A\sin B\ne0\), find the exact value of \(\cot A\cot B\).[3]
- Given that \(B\) is a reflex angle and \(\cot B=3\), find the exact value of \(\cos2B\).[2]
Solution:
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Answer:(a) \(p=\sqrt6,\ q=\sqrt2\) (b) \(\frac95\) (c) \(\frac45\)
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