To begin with, the amplitude of the sine curve, according to the graph, is 70 at the maximum. So far far what you know is
y = 70 sin(something)
Next a full sine wave occurs after 15 seconds approximately. That means after 15 second, you should get 2*pi. Call the values along the x axis = t
y = 70*sin(t/15 * 2*pi) That should be your full answer. Check it out. Where is the maximum? It is just under 4 seconds. It's an estimation. It's not easy to read, but call it 3.9
y = 70*sin(3.9/15 * 2pi) Multiply 2 * 3.9
y = 70* sin(7.8/15 * pi) Multiply 7.8 * pi: Use 3.14 for pi
y = 70 * sin(24.49/ 15)
y = 70* sin(1.633) Make sure you are in radians for the next step.
y = 70*0.99806 = 69.86 inches. which is pretty close to 70.
If this is homework, be sure and point out that the graph is not really accurate and that the end number on the x axis should be 24 not 22.
y = 70 sin (t/15 * 2pi) <<<< answer.
