Vector directions this time on “Learn Physics.” Normally we use the standard math system where you have zero degrees corresponding to the positive x-axis – or east – and then you go clockwise from there – this is 90 this is 180 this is 270 this is back to 360. Works really well when you’re doing sine and cosine and tangent because you learn that in your math class but when you’re dealing with navigation – navigation is all about this – north is zero and it follows the clock. North=zero degrees clockwise to 90 180, 270 and 360. Headings. We’re talking about that. Headings – heading of one two zero – 120 degrees is 0 – 90 – 120 degrees in this second quadrant here so this would be like the first quadrant. That’s the second. That’s the third. That’s the fourth. Here, this is the first, second, third and fourth. In your math class they prefer that you use 0 radians, half pi radians, pi radians, pi and half radians, and 2pi radians because radians are real and degrees are completely invented random dumb things. But but this is what we tend to use. So navigation again – 0 all the way around to 360 starting at the North. Start out at zero degrees, 90, 180 is straight back toward you. 270 is to the left that is West and then 360 is north again. Same as 0. For navigation problems with riverboats and submarines and airplanes we’ll be using this. And for the rest of the problems we tend to use this standard math system. Either one works fine. This one’s really good when you’re dealing with sine cosine and tangent. This one is more real and something we actually use navigation so we switch to this.