어느 지방에는 철도가 있다. 이 철도는 정확히 남북으로 뻗어 있고, 북쪽에 있는 A역과 남쪽에 있는 B역을 잇는다. 어느 날, 20m/s의 속력으로 동풍이 불었다. 그리고 이날, A역행 전기기관차가 시속 90km의 속력으로 달렸다. 그러면 이 기관차에서 나오는 연기의 속도는? (속'도'니까 방향까지 구해야겠죠?)
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Severity: Warning
Message: mkdir(): Permission denied
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File: /volume1/web/PhpstormProjects/www_polymath_co_kr/application/libraries/Common.php
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Function: mkdir
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Function: require_once
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Filename: libraries/Common.php
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File: /volume1/web/PhpstormProjects/www_polymath_co_kr/application/libraries/Common.php
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Function: file_put_contents
File: /volume1/web/PhpstormProjects/www_polymath_co_kr/application/libraries/Common.php
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Function: getLatexImg
File: /volume1/web/PhpstormProjects/www_polymath_co_kr/application/views/ver3/inc/view_comment_list.php
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Function: parseLatexImg
File: /volume1/web/PhpstormProjects/www_polymath_co_kr/application/views/ver3/inc/view.php
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Function: view
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Function: require_once