K. Nicole Clark                                                                                            MATH 311-200

2/6/04                                                                                                                   Dr. Fulling

1.1.12 – Revised

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(a) We want to prove

 

               and 

 

starting from

 

               

 

From this equation, we can say that

 

                

 

Using trig identities, this may be rewritten as

 

                

 

thus,        

 

               

 

Using the same methods

 

           

 

           


(b) Using

 

            1.

            2.

 

            3.

 

we want to express

 

                as

           

 

and vice versa.

 

Using 1.,      becomes

 

                

 

To convert constants A and B to C and D, we assume that

 

           

 

which means     

 

 

 

 

Now, going from    

 

           

to

              

 

we will use similar methods.

 

              

 

The equation was rewritten by substituting the identities for cos and sin into the original equation.

 

Now, we will group the e’s with common exponents together, factoring out the constants.  In order to make the original equation look like the new equation, we will rewrite the constants containing C and D, as constants A and B.

 

These substitutions allow the final equation to be