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# How do I do this? (C3) watch

1. temporary dumbness.
2. All of these questions are the same

what is the minumum value that cos X can be?

so what is the minimum value of 5 cos X

and therefore minimum value of f(t)
3. I got 10 + 5(cos(15t)-53.1)
4. (Original post by gdunne42)
All of these questions are the same

what is the minumum value that cos X can be?

so what is the minimum value of 5 cos X

and therefore minimum value of f(t)
but i get the minimum value as -5.
so cos(15t) - 53.1 = 180???????????????
5. How'd you do it then?
6. (Original post by Get Cape.Wear Cape.Fly.)
but i get the minimum value as -5.
so cos(15t) - 53.1 = 180???????????????

part c
10 + (-5) =

part d
cos ((15t) - 53.1) = -1
7. The minimum is 5 because it's 10-5 =5 because cos(15t)-53.1)=-1

for d) it's 15t-53.1 =180 because you inversed it already so you don't need cos there.
then you find t.
8. ok i got it
9. (Original post by Get Cape.Wear Cape.Fly.)

These are my previous answers: 3cos(theta) + 4sin(theta) = R(cos(theta) -53.1)

Maximum value = 5
The value for which it occurs = 53.1

How do I do c) and d)?
For c) minimum when cos(15t-53.1) = -1 ( what is the minimum value in the cosine graph? )

For d) minimum when 15t- 53.1 = 180 ( again using the cosine graph)
10. (Original post by FZka)
For c) minimum when cos(15t-53.1) = -1 ( what is the minimum value in the cosine graph? )

For d) minimum when 15t- 53.1 = 180 ( again using the cosine graph)
yep i already got it, no worries.
11. (Original post by Get Cape.Wear Cape.Fly.)
yep i already got it, no worries.
Okay, good luck.

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