Math Is Fun Forum
  Discussion about math, puzzles, games and fun.   Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ • π ƒ -¹ ² ³ °

You are not logged in.

#2 Re: Help Me ! » Square Root of a square of a cross product » 2015-12-10 20:36:18

OK I got that (It should be the case), but I want to know if that is a vector rule? if yes can you give me a resource where I can understand why its like that and more.

zetafunc Thanks

#3 Help Me ! » Square Root of a square of a cross product » 2015-12-10 08:26:00

Replies: 4

Hi I got a problem

Let a and b be two vectors...
(a x b) = |a| |b| sin(t) n

where  t is the angle between the two vectors a and b ,and  n is the unit vector in the direction as per right hand rule.

If I square the equation
(a x b)^2 = |a|^2 |b|^2 (sin(t))^2 n^2

(a x b)^2 = |a|^2 |b|^2 (sin(t))^2

Now if I take the square root of both the sides

(a x b) = |a| |b| sin(t)  ...which is the problem LHS is vector and RHS is scaler

I think there is some rules for vectors which I didn't follow may be... but what please explain and give me some reference where I can read more about this.


#5 Help Me ! » Integration problem » 2014-10-09 06:43:57

Replies: 2

Well I solved this in two ways ,one of them is wrong or what I dont know

First answer is

Which is correct as many book have them
But if I try to put  1 = tan(pi/4) and then try to solve it I get something else

I am not able to understand it ,can anybody explain me where I am wrong.....


#6 Re: Help Me ! » Radius of a circular section of a sphere » 2014-01-23 03:50:03

Well I did it like this
By equation of the sphere its already given that the sphere is at origin (0,0,0).
Now from there we get radius of the sphere is

Now we have to find the distance 'd' of the plane
from origin
and that will be

Now use Pythagoras theorem to find the radius of the section by the plane

Good Luck smile

#8 Help Me ! » Radius of a circular section of a sphere » 2014-01-20 19:33:56

Replies: 7

Find the radius of the circular section of sphere

by the plane

My answer came out to

Did I did it correctly,I am bit confused over the question.


#9 Re: Help Me ! » Trigonometric equation problem... » 2013-07-23 01:33:50

Hi bob

When I  solve the equation

my answer is

And when I solve the equation

my answer is

Now which one is correct ,are both correct?

Now putting the different values for "n" we can get the value for theta and put it in the equation and check,but I did just a couple and I know if I can graph it it will show but which application to use for this kind of job I dont know.


#10 Help Me ! » Trigonometric equation problem... » 2013-07-22 23:20:43

Replies: 3


I know that

1) The general solution for



2) The general solution for



Now my question is, in an equation like

,which way should I select i.e.. its in both the forms


in that case we rewrite the equation

Thanks smile

#11 Re: Help Me ! » Physic math problem » 2013-06-11 19:53:59

Yes stefy I agree with you,  but still we use approx symbol for that... don't we ?,in the book they directly used equal symbol.

Bob the topic was about... calculating vectors...
Their are two force vectors given,first one 70N north and another is 50N south west,so calculate the resulting force and direction.

#12 Re: Help Me ! » Physic math problem » 2013-06-11 05:02:17

Well,I thought that but in that case physics books use

approx symbol in general.

So I am right with the math ?

#13 Help Me ! » Physic math problem » 2013-06-11 03:59:09

Replies: 6

In a physic book I found this

Is the math correct ? as far my math goes it should be 1.02

Thanks smile

#14 Re: Help Me ! » Trigonometry Problem » 2013-06-07 05:32:38

Yes dude it make sense now ,I tried to solve and after coming to this point I gave up

Thanks anonimnystefy and Bob for the help...

#15 Re: Help Me ! » Trigonometry Problem » 2013-06-07 02:57:36

And thanks Bob and anonimnystefy for the reply

#16 Re: Help Me ! » Trigonometry Problem » 2013-06-07 02:55:33

Sorry for late reply...
Here is how I did

The answer in the book is sin(a + b) = 24/25 as bob got 0.96,@Bob but I didn't understood what you did... can you explain and why my equation is not working

#17 Help Me ! » Trigonometry Problem » 2013-06-06 20:22:48

Replies: 11

Hi, guys

I tried but I can't  solve it...

If a,b are two different values of x lying between 0 and 2 pi (i.e.. 0 to 360 degrees) which satisfy the equation 6 cos x + 8 sin x = 9 ,find the value of sin(a + b).

Well what I did was I turned that equation into an quadratic equation and find the roots and also use the relation of the sum of the roots.But no luck my solution is getting no where....

here is what I got when I turned it into an quadratic...


#18 Re: Dark Discussions at Cafe Infinity » Which Graphic Card and Laptop » 2013-05-21 03:39:36

I will  purchase a laptop (Dell Inspiron 14R) with it installed.The over all cost seems ok.

Nvidia GeForce GT 730 M is designed for laptops/notebooks,for desktop their are other series both from AMD and Nvidia like Nvidia GTX series is best on desktop platform ,for future I am planning to buy a graphic card from GTX series for my desktop.

#19 Re: Help Me ! » Trigonometric Prove » 2013-05-21 03:26:30

I was bit busy with my studies so I didn't reply...
Yes ,bob it worked

Thanks again

#20 Re: Dark Discussions at Cafe Infinity » Which Graphic Card and Laptop » 2013-05-20 19:29:58

Well after more search I found Nvidia 730M doesn't support four non gaming DirectX 11.1 features ,two of them are for 2D which I don't need in my 3D programming and other two seems to be not very useful for my 3D work.The plus point of nvidia is I get features like Optimus, PhysX, CUDA, 3D Vision, FXAA, TXAA, OpenCL, Direct Compute,and much more which could be explored in 3D programming...

So I am going for Nvidia ,I am not concluding AMD is bad but at this very moment the over all advantages is given by Nvidia

Thanks bobbym and Agnishom

#22 Re: Dark Discussions at Cafe Infinity » Which Graphic Card and Laptop » 2013-05-19 23:35:41

Thanks Agnishom and also thanks to bobbym for that information about CUDA

#23 Re: Dark Discussions at Cafe Infinity » Which Graphic Card and Laptop » 2013-05-19 23:31:32

Thanks for the reply.

I think NVIDIA GeForce GT 730M score 2 points as its a bit better than AMD Radoen HD 8730M in performance and also it have drivers for linux which are better than ADM's drivers.

But I see AMD Radoen HD 8730M support full DirectX 11.1 in case of NVIDIA GeForce GT 730M it only support some features of DirectX 11.1,that's what making me thinking ,as for 3D development its better to have full DirectX 11.1,but again NVIDIA GeForce GT 730M have PhysX which is an another area I would like to explorer...

Any suggestions ....

#24 Dark Discussions at Cafe Infinity » Which Graphic Card and Laptop » 2013-05-19 20:32:35

Replies: 13

I am going to buy a laptop ,is Dell Inspiron any good ...

Two models are quite good for my needs Dell Inspiron 14R and Dell Inspiron 15R
what you guys think about it?

The two models differ in screen size and graphic cards ,the screen size doesn't matters much for me but the graphic card does,so I have two choices

1) NVIDIA GeForce GT730M  2GB VRAM
2) AMD Radoen HD 8730M 2GB VRAM

Both cards are almost similar,so I am confused what should I do...


#25 Re: Help Me ! » Trigonometric Prove » 2013-05-14 18:09:21

Sorry for the late reply...

Thanks Bob I will try it.

Board footer

Powered by FluxBB