O-LevelAdditional MathematicsTrigonometry4037/21 · May/June 2010 · Q46 Marks
Given that sinx = p and cosx = 2p, where x is acute, find the exact value of p and the value of cosecx.
- (a)Given that sinx = p and cosx = 2p, where x is acute, find the exact value of p and the value of cosecx.[3]
- (b)Prove that (cotx + tanx) (cotx − tanx) = 1/sin²x − 1/cos²x.[3]
Mark scheme
Marking points from the official mark scheme (May/June 2010). The mark or mark type is shown in brackets.
- [B1] (a) p² + (2p)² = 1 or cot x = 2
- [B1] (a) p = 1/√5 or cosec² x = 1 + cot² x ⇒ cosec x = √5
- [B1√] (a) cosec x = √5 or p = 1/√5
- [B1] (b) cot²x - tan² x oe
- [M1] (b) cosec² x – 1 – (sec² x – 1) or other relevant use of Pythagoras
- [A1] (b) Correctly reaches conclusion 1/sin²x – 1/cos²x
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