 So it's useful in a number of different disciplines to be able to resolve forces into different reference planes. What that means is, well, if I had a force acting on this sheet of acrylic in this direction, so I was pushing the sheet in this direction, but let's suppose the sheet had some sort of support mechanisms which acted horizontally and vertically. What I would need to do to know what the force is going through that support mechanism, the force is going through the support mechanisms, would be to resolve this force into its horizontal and vertical components. So I'd have to resolve this force into a new reference plane, horizontal and vertical. To do that, I'd need to know what angle I was turning the force through, so some angle of theta degrees. So to do that, to find the vertical and horizontal component of this force, what I'd need to do is use trigonometry. So the trig functions, if you remember, if I assume my force is the hypotenuse of a right angle triangle, and this is the angle I'm interested in, theta, then this side is the adjacent and this side is the opposite. And the trig functions are, of course. So providing I knew the angle and the hypotenuse, the force that I was interested in, I could work out what the vertical and horizontal components are. So instead of using A and O here and H, I could write it like this. So I could write it like this where I have the horizontal component of my force over the force or the vertical component of my force equal to this. That means if I just multiply both sides by the force, it would look something like this where f sin theta is the horizontal component and f cosine theta is the vertical component. It's important to know which angle you're talking about in this right angle triangle because if you're actually talking about this angle here, these would switch over. So you're just going to be careful about what the angle is that you're using in this to resolve your forces. So the horizontal component and the vertical component could replace f on a force diagram. So let's go through an example with some numbers. Let's say I had a 100-kiloneetian force acting at 50 degrees from the vertical, and I wanted to know what the vertical and horizontal components of that force were. Well, the vertical component is equal to the force multiplied by cosine 50. So 100 cosine 50. And the horizontal component is equal to the force sine of the angle. So this is 100 sine 50. And if we put those numbers into our calculators, what we get out is the vertical component is equal to 64.3 kilonewton, and the horizontal component is equal to 76.6 kilonewton. So we can replace that in a force, this 100-kiloneetian force in a force diagram with just the vertical and the horizontal component. So you realize that these don't add up to 100. They're not supposed to. They're distinct components of that 100-kilonewton force.