Cogito
AP Calculus BC · Chapter 8 · Lesson 1
Euler's Method
Following a slope field numerically.
12 problems · about 22 minutes · FUN-7.C
Figure — use these to answer the problems
- The equationdy/dx = a·y
- Through(0, 1)
Warm Up
Straightforward practice. Get the method working first.
5 problemsy = 3, slope 4, step 0.5. What is the new y?
AnswerWhy does Euler underestimate a concave-up solution?
- The tangent line lies below a concave-up curve.
- Because of rounding.
y = 2, slope 3, step 0.5. New y?
Answery = 5, slope 2, step 1. New y?
Answery = 10, slope −3, step 0.5. New y?
Answer
Build It Up
The same ideas with more to keep track of.
3 problemsDoes a smaller step size improve accuracy? 1 yes, 0 no.
AnswerOn a concave-up solution, does Euler over- or underestimate? 1 over, 2 under.
AnswerGoing from x = 0 to x = 2 with step 0.5. How many steps?
Answer
Stretch Yourself
Mixed problems. Work out what kind of question it is before you start.
4 problemsPut one Euler step in order.
Write 1 to 4 in the boxes to put these in order.
- Evaluate the slope at the current point.
- Multiply that slope by the step size.
- Add the result to the current y.
- Advance x by the step size and repeat.
y = 4, slope 6, step 0.25. New y?
AnswerThe First Step
dy/dx = y with y = 1 and a step of 0.5. What is the new y?
AnswerThe Second Step
From y = 1.5 with slope 1.5 and step 0.5. What is the new y?
Answer