Q217 · Practice questionTechnology-freeComplex familiar5 marks
QUESTION 217 (5 marks)
Let , with angles in radians.
a)[3 marks]
Determine I exactly using integration by parts.
b)[2 marks]
Without decimals, show using the curve shape.
WORKED SOLUTION
5 marksPractice marking scheme
ANSWER
(a) . (b) The curve is strictly above its endpoint chord.
Worked solution
(a) Use u=arctan x and dv=dx:
The remaining integral follows by substitution.
(b) For x>0 the second derivative is . Strict concavity places the curve above the chord from (0,0) to (1,pi/4) on the interior. The chord encloses area pi/8, so integration gives the strict inequality.
Equivalent mathematically justified methods accepted.
Exact answers unless a decimal accuracy is specified.
Part a: Choose suitable parts.
Part a: Integrate the rational term.
Part a: Evaluate the exact answer.
Part b: Establish concavity or the strict chord inequality.
Part b: Compare with the triangle area pi/8.
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