Find the exact value of ∫(from 0 to π/4) sinx(4 sinx + 6 cos x) dx.
- (a)Find the exact value of ∫(from 0 to π/4) sinx(4 sinx + 6 cos x) dx.[5]
- (b)Given that ∫(from 0 to a) (6 / (3x + 2)) dx = ln 49, find the value of the positive constant a.[5]
Mark scheme
Marking points from the official mark scheme (Oct/Nov 2017). The mark or mark type is shown in brackets.
- [B1] Obtain 2 - 2cos2x as part of integrand
- [B1] Obtain 3 sin 2x as part of integrand
- [M1] Integrate to obtain form k₁x + k₂ sin 2x + k₃ cos 2x
- [A1] Obtain 2x - sin 2x - ½cos2x or 2x - sin 2x + 3 sin² x
- [A1] Apply limits to obtain ½π + ½
- [B1] Integrate to obtain 2ln(3x+2)
- [*M1] Use at least one relevant logarithm property
- [A1] Obtain (3a+2)/2 = 7 or (3a+2)²/4 = 49 or equivalent without ln
- [DM1] Solve relevant equation to find a
- [A1] Obtain a = 4 only
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