# sketching graphs

• Mar 16th 2009, 02:09 AM
jvignacio
sketching graphs
Hi guys, just having few problems sketching

f(x) = sin(2x)

i basically did a table

x -2 -1 0 1 2
y

and input the x values into the equation to get a y value but then i try graph it on "GraphFunc online" and it gives me different y values for the same x values. Any ideas? i know what a sin sketch looks like but then i dont know how to include the 2x etc .....
• Mar 16th 2009, 03:52 AM
mr fantastic
Quote:

Originally Posted by jvignacio
Hi guys, just having few problems sketching

f(x) = sin(2x)

i basically did a table

x -2 -1 0 1 2
y

and input the x values into the equation to get a y value but then i try graph it on "GraphFunc online" and it gives me different y values for the same x values. Any ideas? i know what a sin sketch looks like but then i dont know how to include the 2x etc .....

The period of y = sin(kx) is $\displaystyle \frac{2 \pi}{k}$. In your case k = 2 so the period is $\displaystyle \pi$. The graph of y = sin x is therefore dilated by a factor of 1/2 in the horizontal direction.

If you're using a table of values to assist your sketching efforts, you should use values of x such as -pi/2, -pi/4, 0, pi/4, pi/2 rather than the values you have chosen ....