{"id":959,"date":"2025-11-21T17:23:25","date_gmt":"2025-11-21T08:23:25","guid":{"rendered":"http:\/\/saegil-lab.kr\/?p=959"},"modified":"2026-03-11T19:33:39","modified_gmt":"2026-03-11T10:33:39","slug":"%ec%82%bc%ea%b0%81%ed%95%a8%ec%88%98-fx-cos-x-%ec%9d%98-%eb%af%b8%eb%b6%84","status":"publish","type":"post","link":"https:\/\/saegil-lab.kr\/?p=959","title":{"rendered":"\uc0bc\uac01\ud568\uc218 f(x) = cos x \uc758 \ubbf8\ubd84"},"content":{"rendered":"\n

<\/p>\n\n\n\n

  <\/span>   <\/span>\"\[ f(x) = \cos x \]\"<\/p><\/p>\n\n\n\n

  <\/span>   <\/span>\"\begin{align*}f'(x) &= (\cos x)' = \lim_{h \rightarrow 0} \frac{\cos (x+h) - \cos(x-h)}{2h} \\& = \lim_{h \rightarrow 0} \frac{(\cos x \cos h - \sin x \sin h) - (\cos x \cos h + \sin x \sin h) }{2h} \\& = \lim_{h \rightarrow 0}\frac{-2 \sin x \sin h}{2h} \\& = -\sin x \times \lim_{h \rightarrow 0}\frac{\sin h}{h} \\& = -\sin x\end{align*}\"<\/p><\/p>\n\n\n\n

\uc5ec\uae30\uc5d0\uc11c \ub2e4\uc74c \uacf5\uc2dd\uc744 \uc0ac\uc6a9\ud558\uc600\ub2e4.<\/p>\n\n\n\n

  <\/span>   <\/span>\"\[ \cos(\alpha \pm \beta) = \cos \alpha \cos \beta \mp \sin \alpha \sin \beta \]\"<\/p><\/p>\n\n\n\n

  <\/span>   <\/span>\"\[ \lim_{h \rightarrow 0} \frac{\sin h}{h} = 1 \]\"<\/p><\/p>\n","protected":false},"excerpt":{"rendered":"

        \uc5ec\uae30\uc5d0\uc11c \ub2e4\uc74c \uacf5\uc2dd\uc744 \uc0ac\uc6a9\ud558\uc600\ub2e4.        <\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[13],"tags":[74,73],"class_list":["post-959","post","type-post","status-publish","format-standard","hentry","category-13","tag-cos-x-","tag-73"],"_links":{"self":[{"href":"https:\/\/saegil-lab.kr\/index.php?rest_route=\/wp\/v2\/posts\/959","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/saegil-lab.kr\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/saegil-lab.kr\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/saegil-lab.kr\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/saegil-lab.kr\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=959"}],"version-history":[{"count":2,"href":"https:\/\/saegil-lab.kr\/index.php?rest_route=\/wp\/v2\/posts\/959\/revisions"}],"predecessor-version":[{"id":961,"href":"https:\/\/saegil-lab.kr\/index.php?rest_route=\/wp\/v2\/posts\/959\/revisions\/961"}],"wp:attachment":[{"href":"https:\/\/saegil-lab.kr\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=959"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/saegil-lab.kr\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=959"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/saegil-lab.kr\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=959"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}