more math questions

[Locke]

These are the ones I'm having trouble with. Any help would be much appreciated. Thanks.

using f(x+h)-F(x)/h
F(x)=1/x^2
what is
F(1/x^2+h)-(1/x^2)/ h
Not too sure what the first step would be


2x+5 -3<x<0 that should be -3 is less than or equal to x
f(x)=-3 x=0
-5x x>0
I need to find the domain and intercepts. How do I go about doing that in these equations.


The volume V of a right circular cylinder of height h and radius r is
V=pi r^2 h. If the height is twice the radius, express the volume V as a function of r


1-cos^2 20 - cos^2 70 find exact value

given sin 30=1/2 use trig identities to find value of
cos 60
cos^2 30
csc pi/6
sec pi/3

The minuite hand of a clock is 6in long. How far does the tip move in 15 min? I think this is an arc length question. S=r degree symbol 0.

[Peetster]

For your clock question:

15 minutes is 1/4 of the circumference of a complete circle.

2*pi*r/4=
2*pi*1.5 in=
3 pi inches

[Frozen North]

For the first problem:
You need to find what f(x+h) is before you can solve. Just plug (x+h) into f(x)=1/x^2 just like you would a normal number, so it'll be f(x+h)=1/(x+h)^2. Shouldn't be too hard after that.


Would you mind clarifying the second problem, is that y=2x+5 (what's the -3 doing there?), f(x)=-3, x=0, (-5x?) and x>0?

f(x)=3: "f(x)" is synonymous with "y" so it's just y=-3

finding the domain: find all of the possible x-coordinates (don't be too proud to draw a graph )
finding the intercepts: set x=0 to find the y-int and y=0 to find the x-int.

Third problem:
It looks too easy so I'm not sure my answer is correct. It's given that h=2r so replace h with 2r leaving you with V(r)= pi*r^2*2r

[Locke]

Thanks for the help so far. Sorry bout the piecewise equation its supposed to look like this

I cant seem to get the piecewise equation to post correctly. I'll work on that.

the book has an answer to the cylinder problem as 2*pi*r^3 I get it now.

[Locke]

one more.

The diameter of each wheel of a bike is 26 in. if you are travelling at a speed of 35mph, how many revolutions per minite are the wheels turning.

My big question is how do you know how to set it up? I think the angular speed formula is used. w=angle/t

[Frozen North]

Nothing fancy needed in this one, they just want you to know how to convert units of measure (mi./hr. ---> mi./min. ---> mi./sec. ---> ft./sec.)

Your math book will probably explain how to do that better than myself.

[JadziaDax]

First, you need the circumference of the bike wheel. With the circumference you know how many inches the wheel goes in one rotation.

In one hour, the bike goes 35 miles. Convert miles to inches (1 mile = 5280 feet, 1 foot = 12 inches). That's how many inches in one hour (60 minutes) the wheel travels.

divide the inches traveled by the inches in 1 rotation (also divide by the fact that there are 60 minutes in 1 hour) and you will be left with # of rotations per minute.

[(35*5280*12)/(26pi*60)] = answer

At least this is what I get from reading your wording of the problem. (I'm also extremely tired right now, so my words might not make any sense)

[Grothendieck]

ah Jadzia... ever the mathematician, making your (mathematical) claims with a caveat... *chuckles*

[JadziaDax]

Well, Grothendieck, I didn't see you give http://www.tfproject.org/tfp/showthr...threadid=27099 a try.

[Grothendieck]

Umm... Should I?

[Sapper]

Not that many people on here mind or anything .... but do you do any of your own homework, Locke?