Can someone help me with Math

[Lillen]

Thanks for the clear up.. i understand chapter one in the book completely. Next is chapter two, i already figured out the radius and radians... now lets move on to how to recognize a periodic curve.

3 sin x makes the curve "hills" and "valleys" expanded to 3 and -3
sin 3x makes the interval 3 times 360 or gives the peroidic curve 1080
sin (x+30) pushes the curve to the left with 30 degrees

what more??

 

[Tinker Grey]

I don't know if this is what you meant but sin(3x) completes a full cycle in 1/3 the time of sin(x). That is, it completes a full cycle in 120 degrees. Sin(x/3) takes 1080 degrees to complete a cycle.

Don't forget sin(x-30) and sin(x)/3.

 

[Lillen]

I don't know if this is what you meant but sin(3x) completes a full cycle in 1/3 the time of sin(x). That is, it completes a full cycle in 120 degrees. Sin(x/3) takes 1080 degrees to complete a cycle.

Don't forget sin(x-30) and sin(x)/3.

Oh í stand corrected, ofcourse... sin 3x = a period of 120, and sin 1/3x = a period of 1080 degrees... slarvfel... negligence error...

 

[Lillen]

sin (x-30) is a curve moved to the right of the origio...

 

[Lillen]

In one of the problems in my book we should decide the value of sin v if cos v = 0.3 were 0 degrees <_ v <_ 90 degrees

Help me understand this...

 

[Tinker Grey]

In one of the problems in my book we should decide the value of sin v if cos v = 0.3 were 0 degrees <_ v <_ 90 degrees

Help me understand this...

If cos(v) = 0.3, then arc-cos(0.3) will give you an angle. Put that value in your calculator and press the sin button.

Alternately, you could realize that cos (v) = a/h, where a is the adjacent side and h is the hypotenuse. Simply apply the Pythagorean theorem by letting h = 1, and a be 0.3. Finding the other side will give you the value of sin, that is, o/h where o is the other (or opposite) side and h is the hypotenuse.

 

[driewerf]

In one of the problems in my book we should decide the value of sin v if cos v = 0.3 were 0 degrees <_ v <_ 90 degrees

Help me understand this...

So easy.
Remember:

cos²v + sin²v=1
So,
sin²v = 1-cos²v
sin²v= 1- 0.09 = 0.91

sinv = sqrt 0.91 ~0.95

 

[Lillen]

I am not sure i follow you...
arcsin and such isn't covered in my book just sin, cos and tangens!!

Ooh I follow you... @ driewerf

 

[Tinker Grey]

I hadn't thought about it dreiwerf's way, but it's the same thing that I was saying for the triangle.

a[sup]2[/sup] + b[sup]2[/sup] = c[sup]2[/sup]
0.3[sup]2[/sup] + b[sup]2[/sup] = 1[sup]2[/sup] = 1
0.09 + b[sup]2[/sup] = 1
b[sup]2[/sup] = 1 - 0.09
b[sup]2[/sup] = 0.91
b ~= 0.95

 

[driewerf]

I am not sure i follow you...
arcsin and such isn't covered in my book just sin, cos and tangens!!

Ooh I follow you... @ driewerf

Lillen,
you are very lucky I'm doing trigo,ometry at this time, myself. But, in order to succeed, there is only one way
-know your formulas
-do very much exercises
-know your formulas
-do very much exercises
-know your formulas
-do very much exercises
-know your formulas
-do very much exercises
-know your formulas
-do very much exercises

In the end, that's the only way.

 

[Lillen]

I am doing exercises, but discuss these things will make you able to recall or remeber easilier and store information.
I am not asking you to do my math for me, i am simply out there to have conversation so I see similarities, symmetry and remeber the insights given..

sin x * cos x = 0
since the product is 0 one of the factors must be 0
And cos x = 0 were sin x = 1 Which gives us the answer
x=n*90 degrees

 

[Lillen]

Lucky we get a sheet with the formulas in the exam.

sin^2v*cos^2v=1
sin 2v = 2sin v * cos v
sin (u+v) = sin v + cos v * cos v + sin v
and so on...
But if i ever enter higher education such as studing math in the university i need to have these formulas or identities stored in my mind.. So i am repeting every now and then.

 

[driewerf]

sin^2v*cos^2v=1
.

hmmm, no.

 

[GQ Chris]

Wow. I'll be coming here for help with my homework.

 

[Lillen]

+

 

[Lillen]

Intergrals.. can someone hold a lessure for me so i get familiar with it!? I came to chapter 3 in the math D -course... I have trubble understanding and follow up what integrals is and how it can be used. I overslept for the lessure in this...

Share this knowledge to me, as wikipedia dosn't make any sense (it's even harder then reading the schoolbook without assitance)

 

[Koizito]

Intergrals.. can someone hold a lessure for me so i get familiar with it!? I came to chapter 3 in the math D -course... I have trubble understanding and follow up what integrals is and how it can be used. I overslept for the lessure in this...

Share this knowledge to me, as wikipedia dosn't make any sense (it's even harder then reading the schoolbook without assitance)

A teacher once taught me this in a very simple way: "You know derivatives right? This is the opposite of derivatives, like subtraction is the opposite of addition and division is the opposite of multiplication."

Problem is, there is no easy way of understanding them (which means that it isn't intuitive and there isn't any trick to get to them), it's just doing the opposite of what you do in derivatives...

 

[Lillen]

More help is need... Man i been on institutions since i read math, and the nullfied me so i couldn't remeber anything of what i learnt...

This is basic math, and easy for anyone who has a highschool diploma to answer... When you move numbers over the equal-sign how do you do it when it's alot of terms. I usually take one by one which is a huge mistake. for instance:

(3x*5y+6y)/5y=5x+3y
i move 3x first
then *5y
then +6y to the other side (and take reverse the sign before them) something say i cant do that???

So how do you do it? do i take everything within the paranthesis and just swich the / sign to * when i move a factor?

How does it look like when its trignometry, same rules or ?

 

[Nostromo]

In that case you might move the 5y to the other side giving you 3x*5y + 6y = (5x + 3y)*5y

You could also working out the left hand side of the equation, rememebering that (a+b)/c = a/c + b/c :-
(3x*5y)/5y + 6y/5y = 5x + 3y which you can then simplify

You could move the parentheses all in one go first, but it would have to be like :
1/5y = (5x+3y)/(3x*5y+6y) and that's just messy.