McGill University · AEMA 202

McGill AEMA 202 tutoring

Intermediate Calculus: send your chapter so we can check whether we can help before you book.

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Course overview

AEMA 202 at Macdonald Campus develops multivariable calculus using curves, space geometry, vector functions, partial derivatives and multiple integrals. The two-input example below focuses on what a partial rate holds fixed. Send your chapter or a question, even if you haven’t started it, so we can confirm support before booking.

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AEMA 202 topics to review

Parametric and polar curvesVectors and geometry of spaceVector functionsPartial derivatives and multivariable applicationsMultiple integrals

Common difficulties

  • Visualizing surfaces and regions
  • Selecting coordinates and bounds
  • Knowing when a theorem or method applies

What stays fixed in a partial derivative?

Use the numerical position xx in metres and time tt in minutes. In an original local model, T(x,t)=18+2x+3t+xtT(x,t)=18+2x+3t+xt gives temperature in °C. At x=2x=2, t=1t=1, interpret TxT_x and TtT_t with units. An observer moves with dx/dt=0.4dx/dt=0.4 m/min through this point. Is the temperature rate experienced by the observer just TtT_t?

Hint: name the input held fixed

For TxT_x, time stays fixed; for TtT_t, position stays fixed. A moving observer changes both inputs. Their rate is dT/dt=Tx(dx/dt)+TtdT/dt=T_x(dx/dt)+T_t.

Separate the two effects

The partial derivatives are Tx=2+tT_x=2+t and Tt=3+xT_t=3+x. At the point, Tx=3T_x=3 °C/m describes spatial change at fixed time; Tt=5T_t=5 °C/min describes temporal change at fixed position. Along the observer’s motion,

dTdt=(3 ∘C/m)(0.4 m/min)+5 ∘C/min=6.2 ∘C/min.\begin{aligned} \frac{dT}{dt}&=(3\,\mathrm{^{\circ}C/m})(0.4\,\mathrm{m/min})\\ &\quad+5\,\mathrm{^{\circ}C/min}\\ &=6.2\,\mathrm{^{\circ}C/min}. \end{aligned}

The extra 1.2 °C/min comes from moving toward warmer positions. You cannot add 3 °C/m directly to 5 °C/min: multiply the spatial rate by the observer’s signed velocity dx/dtdx/dt first. These derivatives describe the stated model locally, not a claim about measured conditions.

Retry: move against the spatial increase

At x=1x=1, t=2t=2, a different observer has dx/dt=−0.5dx/dt=-0.5 m/min. Find both partial rates and the total rate experienced by that observer. Does moving toward smaller xx necessarily mean their temperature falls?

Check the competing changes

Now Tx=4T_x=4 °C/m and Tt=4T_t=4 °C/min. The total is 4(−0.5)+4=24(-0.5)+4=2 °C/min. Motion contributes −2-2 °C/min, but the temporal contribution is +4+4 °C/min, so the observed temperature still rises. A partial derivative describes a change with the other input fixed; this observer does not hold position fixed.

For a spatial gradient refresher, use the existing directional-rate lesson. Its per-distance/per-time distinction helps with units; the two-input time-dependent model above is a different application.

How tutoring can help

Send the model; your tutor can help identify the inputs and their units if you’re unsure where to start. If support is confirmed, your tutor can ask what stays fixed in each partial derivative, trace a simultaneous change through the chain rule and check the final units. Then change the point and direction of motion and predict which contribution changes sign.

Exam preparation for AEMA 202

For a partial-derivative question, name the fixed input and the rate’s units. When several inputs vary, account for each contribution before combining them. Retry the moving-observer question without the solution and explain the sign of the total rate. Add the other topics on your section’s exam list.

Use your section’s outline to choose the chapters to review. We work through permitted practice and comparable problems, without completing graded assignments or exams on your behalf.

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AEMA 202 · official course reference