Complex Numbers Chapter 2 66 repeatedly, and find exactly 4 fourth roots. We can read the values of 64 in rectangular form from Figure 10.3: V-64=+2 ± 2i (all four combinations of ± signs) or we can calculate them as in Example 2, or we can solve the equation 24 = -64 by computer Example 4. Find and plot all values of -81. The polar coordinates of -8i are r = 8, 0 270°360°k = 3T/2 2Tk. Then the polar coordinates of -8i are 270+360°k = 45°+60°k or (10.5) In Figure 10.4, we sketch a circle of radius V2. On it we plot the point at 45° and then plot the rest of the 6 equally spaced points 60° apart. To find the roots in rectangular coordinates, we need to find all the values of r(cos 0 i sin 0) with r and 0 given by (10.5). We can do this one root at a time or more simply by using a computer to solve the equation 26 = -8i. We find (see Problem 33) Figure 10.4 1 1.366 -0.366i, 0.366-1.366i}. Summary In each of the preceding examples, our steps in finding Vrei were (a) Find the polar coordinates of the roots: Take the nth root of r and divide e+2kT by n. (b) Make a sketch: Draw a circle of radius, plot the root with angle 0/n, and then plot the rest of the n roots around the circle equally spaced 2T/n apart. Note that we have now essentially solved the problem. From the sketch you can see the approximate rectangular coordinates of the roots and check your answers in (c). Since this sketch is quick and easy to do, it is worthwhile even if you use a computer to do part (c) (c) Find the r+iy coordinates of the roots by one of the methods in the examples. If you are using a computer, you may want to make a computer plot of the roots which should be a perfected copy of your sketch in (b). PROBLEMS, SECTION 10 Follow steps (a), (b), (c) above to find all the values of the indicated roots VT 2. 27 VT 1. 3. VI6 5. 4. 6. 7. 32 11. S 10. 12. Section 11 The Exponential and Trigonometric Functions 67 64 14 13. 15. 16 17 19 2+2iv3 20. 21
Permutations and Combinations
If there are 5 dishes, they can be relished in any order at a time. In permutation, it should be in a particular order. In combination, the order does not matter. Take 3 letters a, b, and c. The possible ways of pairing any two letters are ab, bc, ac, ba, cb and ca. It is in a particular order. So, this can be called the permutation of a, b, and c. But if the order does not matter then ab is the same as ba. Similarly, bc is the same as cb and ac is the same as ca. Here the list has ab, bc, and ac alone. This can be called the combination of a, b, and c.
Counting Theory
The fundamental counting principle is a rule that is used to count the total number of possible outcomes in a given situation.
Problems Section 10 number 9. Please answer the questions
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