- #1
mr_coffee
- 1,629
- 1
Hello everyone, when I'm doing these problems i always make sure i put a negative inside the sin(x) function, then just later take it out like
cos(2t)+sin(-2t) = cos(2t)-sin(2t); Because sin is an odd function.
But my professor says f it and never does, for instance here is my work, i came out with the professors answer but he didn't use the negative at all, he just acted as if it was r1 = -9+2i, r2 = -9+2i, rather than r1,2 = -9+/- 2i;
http://suprfile.com/src/1/2dq85j/lastscan.jpg
He does this with all his problems, even in an e-mail, he told me, don't worry about putting the negative sign inside the sin function. So is this true?
THe professors answer was:
y = e^(-9t)(18sin(2t)+3cos(2t))
which is the same as mine once i take that negative sign out of the sin(x)
cos(2t)+sin(-2t) = cos(2t)-sin(2t); Because sin is an odd function.
But my professor says f it and never does, for instance here is my work, i came out with the professors answer but he didn't use the negative at all, he just acted as if it was r1 = -9+2i, r2 = -9+2i, rather than r1,2 = -9+/- 2i;
http://suprfile.com/src/1/2dq85j/lastscan.jpg
He does this with all his problems, even in an e-mail, he told me, don't worry about putting the negative sign inside the sin function. So is this true?
THe professors answer was:
y = e^(-9t)(18sin(2t)+3cos(2t))
which is the same as mine once i take that negative sign out of the sin(x)
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