# polar coordinates examples

To convert from Cartesian to polar coordinates, we use the following identities r2 = x2 + y2; tan = y x When choosing the value of , we must be careful to consider which quadrant the point is in, since for any given number a, there are two angles with tan = a, in the interval 0 2ˇ. For instance in the Cartesian coordinate system at point is given the coordinates $$\left( {x,y} \right)$$ and we use this to define the point by starting at the origin and then moving $$x$$ units horizontally followed by $$y$$ units vertically. Therefore, the actual angle is. Recall that there is a second possible angle and that the second angle is given by $$\theta + \pi$$. So, if an $$r$$ on the right side would be convenient let’s put one there, just don’t forget to put one on the left side as well. LinesSome lines have fairly simple equations in polar coordinates. Find the polar coordinates, 0 less than or equal to theta less than or equal to 2 pi and r greater than or equal to 0, of the following points given in Cartesian coordinates. Look at the face of an analog clock or watch. You might spend som… Select a subject to preview related courses: Using the formulas we have learned, we solve from r and then θ. Use a double integral to find the area of the region inside the cardioid r = 2 + 2\cos\theta outside the circle r = 6\cos \theta , and above the x-axis. Anyone can earn Coordinate systems are really nothing more than a way to define a point in space. We will start first with a set of Cartesian coordinates and learn how to convert to polar coordinates. In this case there really isn’t much to do other than plugging in the formulas for $$x$$ and $$y$$ (i.e. | Common Core Math & ELA Standards, Math Worksheets | Printable Math Worksheets for Teachers, AP Environmental Science: Homework Help Resource, Common Core Math Grade 8 - Functions: Standards, Quiz & Worksheet - The Carbon Cycle and Long-Term Carbon Storage, Quiz & Worksheet - Features of Restoration Comedy Theatre, Quiz & Worksheet - Role of Place in the Marketing Mix, Quiz & Worksheet - Characteristics of ATP Molecules, Introduction to Victorian Literature: Overview of Themes, Style, and Authors. As you enter more points, it will begin to look like a more complete circle. Moreover, many physical sy… The above discussion may lead one to think that $$r$$ must be a positive number. Some of the possible results are listed in the table below. Get the unbiased info you need to find the right school. This needs to be done in order to correctly reference the angle counterclockwise from the positive x-axis. The last two coordinate pairs use the fact that if we end up in the opposite quadrant from the point we can use a negative $$r$$ to get back to the point and of course there is both a counter clock-wise and a clock-wise rotation to get to the angle. The final step is to correct to adjust the angle so that it falls within the θ range for Quadrant IV, which can be accomplished this time by adding 360 degrees. We will also look at many of the standard polar graphs as well as circles and some equations of lines in terms of polar coordinates. To identify it let’s take the Cartesian coordinate equation and do a little rearranging. This leads us into the final topic of this section. To find the value of r, we must use the Pythagorean Theorem. This is not the correct angle however. You are now prepared to tackle the end of lesson quiz. Convert $$\left( { - 4,\frac{{2\pi }}{3}} \right)$$ into Cartesian coordinates. This is not, however, the only way to define a point in two dimensional space. We can now make some substitutions that will convert this into Cartesian coordinates. Now that we know how to convert both ways, let's move onto some examples. This is a line that goes through the origin and makes an angle of $$\beta$$ with the positive $$x$$-axis. credit-by-exam regardless of age or education level. Convert $$r = - 8\cos \theta$$ into Cartesian coordinates. So, this was a circle of radius 4 and center $$\left( { - 4,0} \right)$$. To unlock this lesson you must be a Study.com Member. {{courseNav.course.topics.length}} chapters | Emily has a master's degree in engineering and currently teaches middle and high school science. In this case the point could also be written in polar coordinates as $$\left( { - \sqrt 2 ,\frac{\pi }{4}} \right)$$. 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