The reflex angle θ is such that cos θ = k, where 0 < k < 1.
- (i)(a)Find an expression, in terms of k, for sin θ,[2]
- (i)(b)Find an expression, in terms of k, for tan θ.[1]
- (ii)Explain why sin 2θ is negative for 0 < k < 1.[2]
Mark scheme
Marking points from the official mark scheme (May/June 2014). The mark or mark type is shown in brackets.
- [B1 B1] sin θ = –√(1-k²) B1 rest B1
- [B1] Uses t=s/c → –√(1-k²)/k √ for (i) ÷ k.
- [B1] θ is in 4th quadrant. co
- [B1] 2θ lies between 540° and 720° sin2θ is negative in both these quadrants. co
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