![]() ![]() What if we wanted to have anĮquation for theta, r, and x? x is adjacent to the angle. Sides by r, you get r sine theta is equal to y. To the opposite- which is the y side, which is equal to y. Theta? r is the hypotenuse and y is the opposite. Theta- what deals with the r and the y, with respect to See, if we are given r and y and we want to figure out Theta, how could we get y? Well, let's think about it. How can we express y asĪ function if we wanted to go the other way? If we were given r and Step further, and this is actually something you The opposite- which is y- over the adjacent- which is x. X squared plus y squared is equal to r squared. We say that x squared plus-īecause this distance here is also y, right? This distance here is x. So just going into what weĭid in the last video. The point- was it 3 comma 4? I think it was. General, then you can always solve for the particular. See if we can come up with something general here. And you'll get to theĬoordinates are telling you. Yourself 53.13 degrees counterclockwise from the And polar coordinates, it canīe specified as r is equal to 5, and theta is 53.13 degrees. Is equal to 5, and theta is equal to 53 degrees. Specify this point in the 2 dimensional plane by the point And I already set myĬalculator to degree mode. So we want to do this inverse- let me get the calculator up a To figure it out, without getting my TI-85 out. And most people do not have theĪrctangent of 4/3 memorized. Tangent of theta to the negative power or something? But sometimes I'll write arctanĪs 10 to the negative 1 power. Misleading sometimes, when they write it like this. So the same exact statementĬould be written as tan inverse to the negative 1 power. And then another way to writeĪrctan is often- they'll often write it- I'll write it. This is the same thingĪs the inverse tan of the tangent of theta. And this, of course- theĪrctan of the tangent. You could write it as theĪrctan of the tangent of theta is equal to the arctan of 4/3. Tangent of both sides, you get- well, I'll And depending on yourĬalculator, or the convention you use, you might write this. Which is the x-coordinate,Įssentially just take the inverse tangent ofīoth sides of this. ![]() The opposite- which is really the y-coordinate, which isĮqual to 4- over the adjacent. So which of the trigįunctions uses the opposite and the adjacent? Well, the TOA. Unfamiliar to you, you might want to watch the basic How do we figure out theta? So what do we know here? We know- well, we're tryingīack to SOHCAHTOA. Negative distances, so 5 is equal to r, r is equal to 5. 3 squared plus 4 squared isĮqual to the hypotenuse squared, or r squared. Can we figure out r and theta? Well, r, hopefully, is So we're going to break outĪ little trigonometry and actually just a little Because I think it's kind ofĪbstract now, and might be a little difficult to understand. You know, walk r units in the theta direction. Specify it- maybe, if we can figure out a way to do it. This point- instead of specifying, this is theĬartesian coordinates, this is x comma y- you could also And then they'll end upĪt that same point. ![]() You point them in thisĭirection and you say, walk r units. In- you know, you could always imagine someone But you could specify theĭirection if you call this 0, saying, ok, this is thetaĭegrees, and I want you- I'm going to point you in a degree So you could just as easilyĬonvert to radians. How to convert between degrees and radians. That 0 degrees? And we'll deal with degrees. That direction, and you need to go this far. Just point you in a direction, and then you go a certainĭistance in that direction. Have done this in everyday life, is to say, hey, let me Right and 4 up, or we could have gone 4 up and Where we say the first coordinate is how far in the xĭirection we go, and the second coordinate is how far in the upĪnd down, or the y direction, we go. The x-coordinate, and we call this the y-coordinate, and To that point right there, I have to go to the Well, let me give the Cartesian coordinates for that Point in 2 dimensional space, I just tell you how far in the xĭirection I have to go, and how far in the y direction. And so, Cartesian coordinates-Īnd actually, they can apply to more than just 2 dimensions. That you're hopefully familiar with by now. Might have not realized that they were CartesianĬoordinates, because I never called it that before just now. Has dealt with Cartesian coordinates, even though you ![]()
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