i wish i was a maths genius....:(?

Question

i have a maths portfolio. its going pretty well, but i would like to know if there is a easy way to find the period and the amplitude of a sin and cos graph?

Answer 1

Sabina,

Suppose you have f(x) = A*sin(b*x). Then, the amplitude is |A| (or the positive value) and and period will be (2*pi)/b.

The same for the cosine function.

Answer 2

Put very simply, the amplitude of any regular sin or cos graph is simply "half of the distance between the graph's maximum and minimum values."

Suppose a sin wave (curve) rises as high as 12, and as low as -2. We could deduce that the difference between the max and min is 14 units, so the amplitude is 14/2 = 7 units.

The period of any cos or sin function's graph is found by measuring the distance between "repeats" of the graph. If, say, the first peak occurs over x = pi, and the next peak occurs over x = 3pi, then we can grasp that the period is (3pi - pi) = 2pi.

Naturally, this information can be gleaned from looking at the y = sin(...) or y = cos(...) functions themselves, but that's not what you asked for.

Hope this helps!

Answer 3

for the period, say you have sin[2x]. take the coefficient of x (2) and divide it into 2pi. thatll give you the period. the amplitude just use the coefficient of the sin/cos function e.g. 2sin[x] has an amplitude of 2, or twice the amplitude of sin[x]. when you first learn this stuff its not easy. but then you get to where you can graph it without really thinking about it because you use it so much. good luck hope it helps.

Answer 4

If you have the function
y := A*sin(f*theta);
then the coefficient A is amplitude and the multiplier f is the frequency where theta is an angle of so many radians.
The period is given by 1/f. i.e. the duration of one complete oscillation
On the graph the Amplitute is the max, or min, value and the frequency is the number of of oscillations of the curve in a given range. In the graph just count the number of maxs or min peaks in the range to get the frequency.
Now the period is 1/f

Answer 5

the general expression for a cos or sin function is
f(t)=Asin(2*PI*t/T) or f(t)=Acos(2*Pi*t/T)

by comparing with these generel expressions it easy to find the amplitude A and Period T.

EX:

f(x)=25*sin(25*t)
Amplitude A= 25
============
Period:
2 *Pi/T=25 => T=2*Pi/25
==================

Answer 6

me too.

Cos. Say you have sin(x)
compare the function to A*cos(Bx)
Amplitude = | A | = 1
Period = 2*PI/B = 2*PI

Same for A * sin (Bx).

Answer 7

y=Asin(wt) w is usually greek omega

Aplitude is A and the period is (2 pi)/w

y = Asin(wt + f) f usually greek phi f shifts curve sideways

Answer 8

ME TOO.....