Monday, February 29
Announcements
WeBWorK #7 is now open
Due Wednesday at 9pm
Covers material from “Week 7”—see syllabus online
Solutions to (all versions of) Quiz #3 are online
Pick up your quiz papers in the Math Learning Centre
Quiz #4 will take place here on Friday, March 4 (second half of
class time)
Covers material from “Week 6” and “Week 7”
You must bring your student ID to class on every quiz day
You must take the quiz in the section you’re registered in
Monday, February 29
Clicker Questions
Clicker Question 1
A differential equation
Find all functions y = y(θ) that satisfy the equation
y0
= tan θ + 1.
cos θ
A. y = log |sec θ + tan θ| + C
Old hat
B. y = log |sin θ| + C
The equation is the same as
y0 = (tan θ + 1) cos θ
C. y = sin θ − cos θ + C
D. y = log |sin θ| + θ + C
E. y = sin θ + cos θ + C
= sin θ + cos θ,
so this problem is really the
same as
Z
(cos θ + sin θ) dθ.
Clicker Question 2
A differential equation
Find all functions y = y(θ) that satisfy the equation
y0
= tan θ + 1
cos θ
and the initial condition y(π) = 3.
A. y = sin θ − cos θ + 4
Old hat
B. y = sin θ − cos θ + 2
If y(θ) = sin θ − cos θ + C and
y(π) = 3, then
3 = y(π) = sin π − cos π + C
C. y = sin θ − cos θ + 3θ + C
for any C
D. y = sin θ − cos θ + C for
any C
E. y = sin θ − cos θ + 3θ
= 0 − (−1) + C
= 1 + C,
and so C must equal 2.
Clicker Question 3
A separable differential equation
Solve the differential equation (y2 x − y2 )y0 = 1.
A.
B.
C.
D.
E.
1
y=
log |x − 1| + C
p
y = 3 3 log |x − 1| + C
r
2
3 3x
y=
− 3x + C
2
2
y=
2x − x2 + C
none of the above
First, separate . . .
y2 (x − 1)
dy
=1
dx
1
dx
Z
Zx − 1
1
dx
y2 dy =
x−1
y3
= log |x − 1| + C
3
y2 dy =
. . . then solve for y.
Monday, February 29
“More than Math”
Mondays
Leap Day edition
photo credit: Anthony Poon
Monday, February 29
Storm the Wall
Organized by UBC Recreation since 1978
Largest intramural event in North America; 800+ teams
Teams of 5 (including CoRec); individuals too (Iron Person)
Modest swim, sprint, bike, and run legs (≤
1
2
hour total)
Then get everybody over the 12-foot-high wall!
Also a Community and Alumni Festival (Sunday, March 20)
and a Student-focused Festival (Wednesday, March 23)
They also want volunteers to help run it!
Register by next Friday, March 11
http://www.recreation.ubc.ca/stormthewall/