{"html":"<iframe src=\"https://hatenablog-parts.com/embed?url=https%3A%2F%2Ffortran66.hatenablog.com%2Fentry%2F2025%2F03%2F16%2F214425\" title=\"\u3010\u30e1\u30e2\u5e33\u3011cos(pi/2^n) - fortran66\u306e\u30d6\u30ed\u30b0\" class=\"embed-card embed-blogcard\" scrolling=\"no\" frameborder=\"0\" style=\"display: block; width: 100%; height: 190px; max-width: 500px; margin: 10px 0px;\"></iframe>","title":"\u3010\u30e1\u30e2\u5e33\u3011cos(pi/2^n)","categories":[],"url":"https://fortran66.hatenablog.com/entry/2025/03/16/214425","width":"100%","type":"rich","height":"190","version":"1.0","provider_url":"https://hatena.blog","provider_name":"Hatena Blog","author_name":"fortran66","description":"\u500d\u89d2\u30fb\u534a\u89d2\u306e\u516c\u5f0f\u304b\u3089 sin(2x) = 2sin(x)cos(x)=2sin(x)sqrt(1-sin2(x)) sin2(2x) = 4sin2(x)(1-sin2(x)) t = sin2(x) \u3068\u7f6e\u304f\u3068 4t2-4t+sin2(2x) = 0 \u3053\u306e\u4e8c\u6b21\u65b9\u7a0b\u5f0f\u3092\u89e3\u304f\u3068 sin(x) = sqrt(1-sqrt(1-sin2(2x))) / sqrt(2) \u3053\u308c\u304b\u3089 cos(x) \u3082\u6c42\u307e\u308b\u30021\u00b1cos(2x)\u301csin2(x), cos2(x) \u3068\u4e8c\u6b21\u65b9\u7a0b\u5f0f\u306e\u89e3\u306e\u8907\u53f7\u3068\u304b\u3089\u3082\u308f\u304b\u308b\u3002 x\uff1dpi \u304b\u3089\u59cb\u3081\u3066\u3053\u306e\u516c\u5f0f\u3092\u7e70\u308a\u8fd4\u3057\u9069\u7528\u3059\u308b\u3068\u3001 sin(x/2n)=sqrt(2-sqrt(2+sqrt\u2026","image_url":"https://m.media-amazon.com/images/I/417epV4urLL._SL500_.jpg","published":"2025-03-16 21:44:25","blog_title":"fortran66\u306e\u30d6\u30ed\u30b0","blog_url":"https://fortran66.hatenablog.com/","author_url":"https://blog.hatena.ne.jp/fortran66/"}