# 374bhw8 - i i and they are all real. ( Hint : Remember the...

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HW#8 —Phys374—Spring 2007 Prof. Ted Jacobson Due before class, Friday, April 6, 2006 Room 4115, (301)405-6020 www.physics.umd.edu/grt/taj/374b/ jacobson@physics.umd.edu Fun with complex numbers 1. Express the following in “Cartesian form” x + iy , where x and y are real: 1 / (2 - 3 i ), (1 + 2 i ) / (3 + 4 i ), 5 e 6 i . 2. Express the following in “polar form” re , where r is a real positive number and θ is real: - 6, - 5 i , (1 + i ) / 2, 2 - 3 i , (2 + i ) / (1 + 2 i ). ( Note : Be careful to get the correct sign for the phase.) 3. (i) Find all the cube roots of - 1, i.e. ( - 1) 1 / 3 , and express them all in both polar form and in Cartesian form. (ii) Plot and label them in the complex plane. 4. Show that there are inﬁnitely many values of
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Unformatted text preview: i i and they are all real. ( Hint : Remember the denition of the complex exponential: w z = exp( z ln w ).) 5. Prove Eulers identity e i = cos + i sin as follows: show that both sides of the identity satisfy the same rst order dierential equation, and they are equal for = 0. 6. Prove the trigonometric identities for cos( a + b ) and sin( a + b ) by taking the real and imaginary parts of the identity exp( i ( a + b )) = exp( ia )exp( ib ). You may of course use the fact that exp( i ) = cos + i sin ....
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## This note was uploaded on 12/29/2011 for the course PHYSICS 374 taught by Professor Jacobson during the Fall '10 term at Maryland.

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