Questions regarding last task in Javascript, Numbers

Hello!

I've recently encountered a little bit of trouble with this task. I'm being asked to create a variable named "circumference" and give it a value of Math.PI(diameter). When I press the "check work" button I get the following message:

Bummer! No variable named "circumference" has been defined. Make sure to declare the variable like: var circumference =...

Heres the following code:

var diameter = 5.75, a = 17, b = 42, c = 1337, ageIfILiveToYear2100 = (new Date(2100, 0, 1) - new Date(1995, 5, 16, 7, 20)) / (1000 * 60 * 60 * 24 * 365.242);

var circumference = Math.PI(diameter);

And here's a screenshot of the problem

http://i.imgur.com/EbuzbAZ.png

Thank you in advance!