{"action":"created","issue":{"url":"https://api.github.com/repos/sympy/sympy/issues/9934","labels_url":"https://api.github.com/repos/sympy/sympy/issues/9934/labels{/name}","comments_url":"https://api.github.com/repos/sympy/sympy/issues/9934/comments","events_url":"https://api.github.com/repos/sympy/sympy/issues/9934/events","html_url":"https://github.com/sympy/sympy/issues/9934","id":108734789,"number":9934,"title":"limit on Sum(sin(n).rewrite(exp), (n, 0, k)).doit() is wrong","user":{"login":"asmeurer","id":71486,"avatar_url":"https://avatars.githubusercontent.com/u/71486?v=3","gravatar_id":"","url":"https://api.github.com/users/asmeurer","html_url":"https://github.com/asmeurer","followers_url":"https://api.github.com/users/asmeurer/followers","following_url":"https://api.github.com/users/asmeurer/following{/other_user}","gists_url":"https://api.github.com/users/asmeurer/gists{/gist_id}","starred_url":"https://api.github.com/users/asmeurer/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/asmeurer/subscriptions","organizations_url":"https://api.github.com/users/asmeurer/orgs","repos_url":"https://api.github.com/users/asmeurer/repos","events_url":"https://api.github.com/users/asmeurer/events{/privacy}","received_events_url":"https://api.github.com/users/asmeurer/received_events","type":"User","site_admin":false},"labels":[{"url":"https://api.github.com/repos/sympy/sympy/labels/concrete","name":"concrete","color":"0000FF"},{"url":"https://api.github.com/repos/sympy/sympy/labels/series","name":"series","color":"0000FF"},{"url":"https://api.github.com/repos/sympy/sympy/labels/Wrong%20Result","name":"Wrong Result","color":"e11d21"}],"state":"open","locked":false,"assignee":null,"milestone":null,"comments":8,"created_at":"2015-09-28T19:57:23Z","updated_at":"2015-10-01T05:54:31Z","closed_at":null,"body":"This is related to https://github.com/sympy/sympy/issues/8328, but it's a different code path so it should be a separate issue. \r\n\r\n```\r\nIn [16]: limit(simplify(Sum(sin(n).rewrite(exp), (n, 0, k)).doit().rewrite(sin)), k, oo)\r\nOut[16]:\r\n    sin(1)\r\n─────────────\r\n-2⋅cos(1) + 2\r\n\r\nIn [25]: limit(simplify(Sum(cos(n).rewrite(exp), (n, 0, k)).doit().rewrite(sin)), k, oo)\r\nOut[25]: 1/2\r\n```\r\n\r\nAccording to WolframAlpha, both sums do not converge. I didn't check if the partial sums are correct, but I suspect they are and `limit` is what's wrong here. "},"comment":{"url":"https://api.github.com/repos/sympy/sympy/issues/comments/144628138","html_url":"https://github.com/sympy/sympy/issues/9934#issuecomment-144628138","issue_url":"https://api.github.com/repos/sympy/sympy/issues/9934","id":144628138,"user":{"login":"jksuom","id":6929119,"avatar_url":"https://avatars.githubusercontent.com/u/6929119?v=3","gravatar_id":"","url":"https://api.github.com/users/jksuom","html_url":"https://github.com/jksuom","followers_url":"https://api.github.com/users/jksuom/followers","following_url":"https://api.github.com/users/jksuom/following{/other_user}","gists_url":"https://api.github.com/users/jksuom/gists{/gist_id}","starred_url":"https://api.github.com/users/jksuom/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/jksuom/subscriptions","organizations_url":"https://api.github.com/users/jksuom/orgs","repos_url":"https://api.github.com/users/jksuom/repos","events_url":"https://api.github.com/users/jksuom/events{/privacy}","received_events_url":"https://api.github.com/users/jksuom/received_events","type":"User","site_admin":false},"created_at":"2015-10-01T05:54:31Z","updated_at":"2015-10-01T05:54:31Z","body":"So, instead of the \"limit\" ``cos(oo)`` we could have ``Limits(-1, 1)``."}}