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See how to create the four functions in this practice session.
Resources
 Understanding the Order of Operations: PEMDAS (Please Excuse My Dear Aunt Sally)

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How did it go?

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If you didn't get it to work, you can watch my solution,

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compare it to what you wrote, and then try to recreate it yourself.

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Also, keep in mind there are often different ways to solve

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a programming challenge.

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Your solution may be different than mine and still work, that's fine.

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Okay, first I'll use the script tag to attach this JavaScript file

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to the index.html file.

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Because the geometry.js file is inside a JavaScript folder,

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js, the complete path from the index to the JavaScript file is js/geometry.js.

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Okay, next I'll create a function.

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I use the function keyword followed by the name of the function,

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a pair of parentheses, and then some braces.

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I'll name this areaRectangle.

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You probably used a different name, and that's fine.

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As long as the name clearly indicates what the function does, you're doing well.

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Okay, this function needs two parameters to capture the width and

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height values that are passed to it when the function's called.

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Parameters go inside the parentheses.

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And the programming for the function goes inside the braces.

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The area is just the width times the height, so I'll use a simple return

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statement, That returns the result of this calculation.

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Calculating the volume of a box is pretty much the same.

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It just requires a third parameter, the length.

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Now, calculating the area of a circle requires a bit more JavaScript.

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But I'll start with the basic function structure first.

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This function will only take one argument, the radius of the circle.

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Now, to calculate the area of the circle,

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we need to do some more complex math using the value of pi.

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Fortunately, the JavaScript math object includes the value of pi built into it.

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Math.PI, then to calculate the area, we multiple this by the square of the radius.

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To calculate the square of a value, you can use the Math.pow method.

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Pow stands for power, and it lets you raise the value to a given power.

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In this case, I want to square the radius or

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raise the radius value to the second power.

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The pow method takes the value that you wish to raise,

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here it's the radius, and the value that you wanna raise it to.

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In this case, I wanna square the radius, so I use 2 for this value.

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Now, calculating the volume of a sphere is similar.

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You need to use pi and you also need to use pow.

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But this time you'll raise it to the third power.

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Notice that I wrapped the 4 divided 3 inside parentheses.

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This helps group that mathematical statement and

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makes it clear to me that I'm looking at fourthirds here, or 4 divided by 3.

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Now, this is related to the order of operations,

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something you may remember from a math class.

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I've added a link to the teacher's notes for more information on the order of

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operations, if you're interested in learning more.

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Okay, finally, I just need to call each function.

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Remember to call a function, you use the function's name and a set of parentheses.

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Inside the parentheses, I include the arguments, or values,

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that I want to pass to the function.

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In this case, I'm calling the areaRectangle function, and

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passing the width and the height of the rectangle.

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But I also want to print this to the console, so I use the console.log method.

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Now, do you notice something here?

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I'm actually calling two functions.

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The first function, areaRectangle,

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returns a value that's passed to the second function, the log method.

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Now, this is really a common thing in JavaScript, so

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get used to seeing code like this.

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Now, the last three lines are pretty much the same.

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You're just calling different functions with different arguments.

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I'll save this file and preview it in a browser.

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And then I'll open the dev tools, And check out the console.

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There it is.

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I hope you were able to complete this practice successfully.

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If not, why not start over and

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try to write the program without looking at my version?

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Have fun with JavaScript, and I'll see you again soon.
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