Q279 · Practice questionTechnology-freeSimple familiar6 marks
QUESTION 279 (6 marks)
An ellipse has equation . Point P on its upper half has coordinates .
a)[2 marks]
Use implicit differentiation to determine and its value at P.
b)[2 marks]
Determine a Cartesian equation of the tangent at P.
c)[2 marks]
Sketch the ellipse and the tangent on the blank axes. Label all axis intercepts of both.
WORKED SOLUTION
6 marksPractice marking scheme
ANSWER
(a) ; at P it is . (b) . (c) Ellipse intercepts ; tangent intercepts .
Worked solution
(a) Differentiate: . Hence when . Substitute the given P.
(b) Point-slope form is . The product of the two radical factors is 3, giving intercept 4.
(c) See the solution diagram. The tangent must touch the upper-right part of the ellipse at P and slope downwards.
Equivalent justified methods accepted; respect any requested proof method.
Exact values unless specified. Sketches assessed by mathematical features, not artistic quality.
Part a: Differentiate implicitly and isolate the derivative.
Part a: Evaluate at P.
Part b: Use the point and the correct gradient.
Part b: Obtain an equivalent tangent equation.
Part c: Draw the ellipse with its four intercepts.
Part c: Draw the tangent through P and label its intercepts.
Practice question aligned to the current QCAA syllabus; review the worked solution and marking criteria.
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