Show that 1/(1-sinx) - 1/(1+sinx) = 2tanxsecx.
- (i)Show that 1/(1-sinx) - 1/(1+sinx) = 2tanxsecx.[4]
- (ii)Hence solve the equation 1/(1-sinx) - 1/(1+sinx) = cosecx for 0° ≤ x ≤ 360°.[4]
Mark scheme
Marking points from the official mark scheme (Oct/Nov 2018). The mark or mark type is shown in brackets.
- [M1] (1+sinx)-(1-sinx) / (1-sinx)(1+sinx)
- [A1] 2sinx / 1-sin²x
- [M1] 2sinx / cos²x
- [A1] 2sinx/cosx * 1/cosx = 2tanxsecx AG
- [M1] equate 2secxtanx = cosecx
- [A1] tan²x = 1/2
- [A1] two correct
- [A1] 35.3°, 144.7°, 215.3°, 324.7°
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