







The period T of a pendulum 
20120327 

From Ashley: The period T of a pendulum is given in terms of its length, l, by T=2pi sqrt(l/g) where g is the acceleration due to gravity(a constant)
a. find dT/dl
b. what is the sign of dT/dl
c. what does the sign of dT/dl tell you about the period of the pendulums? Answered by Penny Nom. 





Is 0.1234567891011.... periodic? 
20100223 

From Adriana: 0.1234567891011.......Is this fraction periodic ? Answered by Penny Nom. 





y = sin(x) + 3 
20091110 

From Kapilan: When graphing trigonometric functions like SIN and COSINE does f(x)=x
squared equal to SIN or COSINE
Also what is the range, domain, period and ampliltude for y=sin@ + 3 Answered by Harley Weston. 





Time in a Swing 
20090222 

From Barb: I looked at the questions concerning a pendulum as I know I need to use this formula but I am stiil not able to figure this problem out. Can you help?
If a child is on a swing with a 10 foot chain, then how long des it take to complete one cycle of the swing?
I know I am suppose to use the formula 8T^2 = pi^2 L but I do not understand how to do this.
Thanks Answered by Janice Cotcher. 





What is a group of three numbers within a larger number? 
20081216 

From kim: My daughter brought home a question for math homework. What is a group of three numbers within a larger number? Answered by Robert Dawson and Harley Weston. 





A periodic function 
20081126 

From Ali: A periodic function f(x) has a period of 9, if(2)=3 and f(5)=13, determine the value of f(11)?
tks /rgrds
Ali Answered by Penny Nom. 





The number of hours of daylight 
20080603 

From Marilyn: Hi, could you please help me with this question?
In a city (in the Northern Hemisphere) the minimum
number of hours of daylight is 9.6 and the maximum
number is 14.4. If the 80th day of the year (March
21) has 12 hours of daylight, determine a sine
function which gives the number of hours of
daylight for any given day of the year. (Jan 1 = 1,
Jan 2 = 2, etc).
Thank you! Answered by Harley Weston. 





The swaying of a building in the wind 
20070811 

From San: During a strong wind, a tall builing, such as the CN Tower, can sway
back and forth as much as 100cm, with a period of 10 seconds.
Please help me to determine the equation for this function, in the form
y=asinkx Answered by Stephen La Rocque. 





How many complete cycles does the piston make in 30minutes? 
20070811 

From San: A piston in a large factory engine moves up and down in a cylinder.
The height, h centimetres, of the piston at t seconds is given by formula
h=120sin(pi)t+200
How many complete cycles does the piston make in 30minutes? Answered by Penny Nom. 





Period of a sum of trig functions 
20070617 

From Aakash: the period of the function f(x)=cos3x+sin4x+tan4x Answered by Stephen La Rocque. 





The period of a simple pendulum 
20070310 

From Melissa: The period of a simple pendulum of length L feet is given by: T=2pi(sqrt(L/g))seconds. It is assumed that g, the acceleration due to gravity on the surface of the earth, is 32 feet per second per second. If the pendulum is a clock that keeps good time when L=4 feet, how much time will the clock gain in 24 hours if the length of the pendulum is decreased to 3.97 feet? (Use differentials and evaluate the necessary derivative at L=4 feet.) Answer is in seconds. Melissa Answered by Penny Nom. 





The period of sin(x) + cos(x) 
20050721 

From A student: WHAT IS THE PERIOD OF SIN(X)+COS(X)? Answered by Penny Nom. 





What is a group of three numbers called in a large number? 
20020115 

From Laurie: What is a group of three numbers called in a large number? My son has this question on his 4th grade worksheet. I've taught middle school math for 7 years and nver heard of it. Answered by Paul Betts. 





Finite nonperiodical numbers 
20010327 

From Wouter: Is there anyone who knows the official name for decimal finite nonperiodical numbers such as 0.4 or 0.25 as opposite of numbers like 0.3333333... or 0.28571428571428...? Answered by Penny Nom. 





Period 
19991228 

From Mahdawi: I have attached a diagram of the graph, and I need to find out its period. I really don't understand how to do so, please help! Answered by Harley Weston. 





Graph of a sine function 
19991223 

From Pierre: Given; amplitute:1 period: 540 Phase shift: 60 degree,right I am ask to right the equation: sin 2/3 (value 60degree) When I am asked to graph the equation, the period is mixing me up. Answered by Harley Weston. 

