How can I sketch the graph of y=cos2x?

Answer 1

give x the values -pi/4,-pi/3,-pi/6,-pi/2,-pi,pi,6,pi/4,pi/3,pi/2,pi
find the values of cos 2x
i.e.cos(-pi/2),cos(-pi/6) etc
take it on the y axis and plot

Answer 2

If you really can't do it, sketch axes, then tap into your calculator the values. So pick x=0. Tap in cos0, cos(2*0). Draw the results on your sketch in different colours Then pick x=30. Tap in cos(30), cos(60) which is cos 2x. Draw the results on your sketch in different colours Then pick x=60. Tap in cos(60), cos(120). Draw the results on your sketch in different colours etc. You'll have your graph.

Answer 3

preferably with a pencil, so you can erase your mistakes.

The acceptable method of graphing any function is to set up a table of solution values, and plot the values on your graph.

You already know that -1 <= y <= 1 and the function repeats every pi radians or 180 degrees, right?

Answer 4

i used y=cos(2x) [i hope that's what you meant]

I get a sine wave with an amplitude of 1 and a wavelength of 3(about 3, a little more acutally)

If you can you might want to scale the y-axis by .25 and the x-axis by .5 or 1/3, that should make it easier to sketch.

Answer 5

One way to plot this graph is to vary x from [0 to 360 degrees]. If you recall, the period of cosine(x) varies in this range. In this case, you have 2 times the angle x; when you complete this plot, you will find that you will have two complete cycles of cosine x in this period.

Please note that you can also work this problem using radians [0 to 2pi].

Good

Answer 6

Find the:

period
x and y intercepts
amplitude

From there it should be pretty straightforward. A graph in the interval [-2pi,2pi] should suffice.

Answer 7

for a graph, go to http://www.calculator.com/calcs/GCalc.html

type in cos(2x) or (cos(x))^2, depending if cos(x) is being squared or not

cos(2x) = cos(x)^2 - sin(x)^2 = 2cos(x)^2 - 1 = 1 - 2sin(x)^2