Posted by anna on Friday, August 5, 2011 at 6:21pm.
okay sorry last two questions! I promise!
The sun always illuminates half of the moon’s surface, except during a lunar eclipse. The illuminated portion of the moon visible from Earth varies as it revolves around Earth resulting in the phases of the moon. The period from a full moon to a new moon and back to a full moon is called a synodic month and is 29 days, 12 hours, and 44.05 minutes long. Write a sine function that models the fraction of the moon’s surface which is seen to be illuminated during a synodic month as a function of the number of days, d, after a full moon. [Note: full moon equals illuminated.]
I am really confused on this one I know I have to make a sine function.
so would it be like y= 29sin(pi/6*t)+44.05
sorry that was probably a really bad guess.
2)A bicycle tire has a diameter of 20 inches and is revolving at a rate of 10 rpm. At t = 0, a certain point is at height 0. What is the height of the point above the ground after 20 seconds?
y=20sin(pi/5*20) Is that right?

Precalc  bobpursley, Friday, August 5, 2011 at 8:01pm
period=29 days, 12hrs, 44.05 min.
ok, change that to days: 29+12/24+44.05/(60*24), I get 29.53 days.
y=.5cos(2PI/29.53 * t)+.5 check it. Graph it.
2. it goes up and down over a 20 inch altitude. at t=0, it is at zero.
h=10cos(2PI*10t)+10 is one solution, there are others, depending on where you call h=0. Height at ground level is not always called zero, you could call zero at the top.
Answer This Question
Related Questions
 Precalc(attn Bobpursley)  Hi i posted this before but I wanted to ask ...
 physics  During an eclipse, the Sun, Earth, and Moon are arranged in a line as ...
 Math, Geomertry  A total solar eclipse occurs when the moon passes between the ...
 geometry  A total solar eclipse occurs when the moon passes between the earth ...
 Science  1.Which type of eclipse would you expect to see if the moon passes ...
 Science  1.Which type of eclipse would you expect to see if the moon passes ...
 Science  1. Which type of eclipse would you expect to see if the moon passes ...
 Science HELP PLZ  1. Which type of eclipse would you expect to see if the moon ...
 Science  1. Which type of eclipse would you expect to see if the moon passes ...
 Science  1. Which type of eclipse would you expect to see if the moon passes ...
More Related Questions