The Kirby Plan
Picture by deviantart.com user
This is what we need to do…
1. We have decided on a target, Kirby, and a method of attack,
our evil demon frog, all that’s left is figuring out WHEN to
attack. Kirby needs to eat every 3 hours, for some reason he
NEVER deviates from this pattern. Kirby fills up at a constant
rate for 1.5 hours until he feels full. We are going to rate Kirby’s
hunger on a scale from 1-10, 1 being the hungriest and 10
being when he is the fullest. Kirby first starts to eat at 1:00am.
A. Sketch a sinusoidal graph of Kirby’s eating habits
B. Write a sine and cosine equation for the graph
C. We plan to attack Kirby when he’s at the park at 2:00pm. He
can’t seem to fight with much gusto if his fullness is above 8.
i. Is 2:00pm a good time to attack?
ii. What is a good time near 2:00pm to attack?
It’s graphing time!
• Don’t panic! Let’s take some important
information from the question!
• Kirby needs to eat every 3 hours.
3 hours is our period!
• Rate Kirby’s hunger on a scale from 1-10.
1 is our min and 10 is our max!
• Kirby first starts to eat at 1:00am.
1:00am is going to be our starting point!
Using what we learned in the last slide let’s
make our graph!
NOTE: we are using the 24 hour clock for our x-axis (:
Parts of the Equation!
Parameter What is it?
A- amplitude This is the distance from the minimum or
maximum to the sinusoidal axis.
B- determines It is the distance along the x-axis required
period to make one wave. The period is equal to 3
C: Phase shift This determines the horizontal shift of the
D: Vertical shift It determines the sinusoidal axis.
f(x)= Asin B(x- C) +D
g(x)= Acos B(x- C)+ D
It’s Equation time!
B: 3 So our sin equation is
C: 1.75 f(Kirby)= 4.5sin 2π (x- 1.75) + 5.5
NOTE: Make sure your calculator is in
radians! NOT degrees! Otherwise you’ll
end up with some wonky answers!
Now let’s do cosine!
B:3 So our cosine equation is
C: 1 g(Kirby)= -4.5cos 2π (x-1) +5.5
2:00, good or bad time to attack?
NOTE: We are using
the 24 hour clock.
2:00pm is the
equivalent of 14:00
Let’s try using our cosine equation to
So how do we figure out a good time
1. Write down your equation.
2. Letθ= 3 (x- 1.75) because it makes
our equations easier to work with.
3. Re write the equation using θ.
4. Add -5.5 to both sides of your
5. Divide both sides of the equations by
6. Find the inverse sin of 9 , and were
done! Or are we…
7. Convert θ back to
the original value.
8. Now solve for x!
Lets see if we get the same answer
Now let’s turn 2.03124 into
2.03124 (60)= 121.8744 min
It’s common sense time!
There are 2 hours in 120
minutes, and 1.78 minutes
left over. So that means we
should attack at
approximately 2:02 am.
So When Do We Attack??
How did we do that?!
Well minions the answer to that is quite simple.
Our period is 3 hours, so we added 12 (which is
a multiple of 3) to 02:02 to arrive at 14:02.
TOA (time of attack)= 14:02
Now that have all the math out of the way
it’s time for us to get ready to attack!
SAY GOODBYE KIRBY!