A curve has equation y = 4x + 3 cos 2x. The normal to the curve at the point where x = π/4 meets the x- and y-axes at the points A and B respectively. Find the exact area of the triangle AOB, where O is the origin.
- (a)A curve has equation y = 4x + 3 cos 2x. The normal to the curve at the point where x = π/4 meets the x- and y-axes at the points A and B respectively. Find the exact area of the triangle AOB, where O is the origin.[8]
Mark scheme
Marking points from the official mark scheme (May/June 2015). The mark or mark type is shown in brackets.
- M1,A1 M1 for attempt to differentiate A1 for all correct
- B1 for y
- DM1 for substitution of x = π/4 into their dy/dx and use of 'm₁m₂ = −1', dependent on first M1
- DM1 correct attempt to obtain the equation of the normal, dependent on previous DM mark
- A1 must be terms of π
- A1 must be terms of π
- B1ft Follow through on their x and y intercepts; must be exact values
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