In The Great White North Posted August 5, 2011 Share Posted August 5, 2011 I tried to copy and paste the question but couldn't. Could someone tell me what the "Im" in question 9 means? Quote Link to comment Share on other sites More sharing options...
8filltheheart Posted August 5, 2011 Share Posted August 5, 2011 I just asked ds and he said it means the imaginary part. Quote Link to comment Share on other sites More sharing options...
In The Great White North Posted August 5, 2011 Author Share Posted August 5, 2011 Can you ask him how, without any equals sign, I'm supposed to find it? Quote Link to comment Share on other sites More sharing options...
onaclairadeluna Posted August 6, 2011 Share Posted August 6, 2011 You need to evaluate the expression and take the imaginary part. If for example you get 2 +4i the answer would be 4i just ignore the real part of the expression. Quote Link to comment Share on other sites More sharing options...
kiana Posted August 6, 2011 Share Posted August 6, 2011 Im (z) means the imaginary part of the complex number z. Re (z) means the real part of the complex number z. For example, Im (3 + 4i) is 4. Re (3 + 4i) is 3. I'm not sure what you mean about an equals sign. Quote Link to comment Share on other sites More sharing options...
8filltheheart Posted August 6, 2011 Share Posted August 6, 2011 Ds came back in the room and asked what the actual problem was. I showed it to him and he sat down and worked it out if you want to see the solution. He combined the sin's and cos's to get Im((2cos30 cos 18 + 2isin 30 cos 18)^6)= Im((sqrt 3 cos 18 + i cos 18) ^6)= Im(cos^6 18(sqrt 3 + i) ^6)= Im(cos^6 18 (-4)) = Im(-4cos^6 18)=0 b/c there is no imaginary part. Quote Link to comment Share on other sites More sharing options...
kiana Posted August 6, 2011 Share Posted August 6, 2011 Im(cos^6 18 (-4) ) I believe this should be -64. Final answer's correct though. Quote Link to comment Share on other sites More sharing options...
8filltheheart Posted August 6, 2011 Share Posted August 6, 2011 I believe this should be -64. Final answer's correct though. I just asked him, and he said you are right. He said he dropped a 2 when he was writing it legibly for me to read so that I could type it in, but he didn't notice b/c he knew the outcome of the final answer. I have no idea what he's actually talking about though, b/c this is beyond me. ;) Quote Link to comment Share on other sites More sharing options...
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