{"common":{"save":0,"post_id":"7868","level":2,"total":10,"point":10,"point_extra":0},"segment":[{"id":"8003","post_id":"7868","mon_id":"1159278","chapter_id":"1159328","question":"<p>Cho&nbsp;&Delta;ABC c&oacute; AB = 12 cm, AC = 16 cm, BC = 20 cm. L&agrave;m&nbsp;tr&ograve;n \u0111\u1ebfn \u0111\u1ed9, s\u1ed1 \u0111o g&oacute;c B l&agrave;:<\/p>","options":["<strong>A.<\/strong> 45&deg;","<strong>B.<\/strong> 58&deg;","<strong>C.<\/strong> 53&deg;","<strong>D.<\/strong> 42&deg;"],"correct":"3","level":"2","hint":"","answer":"<p>Ch\u1ecdn&nbsp;<span style=\"color:#16a085;\"><strong>C.<\/strong>&nbsp;53&deg;<\/span><\/p><p>Ta c&oacute;:&nbsp;<span class=\"math-tex\">$AB^2+AC^2=12^2+16^2=400=20^2=BC^2$<\/span>&nbsp;suy ra&nbsp;<span class=\"math-tex\">$AB^2+AC^2=BC^2$<\/span><\/p><p>Do \u0111&oacute;&nbsp;&Delta;ABC vu&ocirc;ng \u1edf A (\u0111\u1ecbnh l&iacute; Pythagore \u0111\u1ea3o).<\/p><p><span class=\"math-tex\">$\\sin B=\\dfrac{AC}{BC}=\\dfrac{16}{20}=0,8$<\/span>&nbsp;suy ra&nbsp;<span class=\"math-tex\">$\\widehat{B}\\approx 53^o$<\/span>.<\/p>","type":"choose","extra_type":"shape1","time":"0","user_id":"127","test":"0","date":"2024-10-21 02:15:18","option_type":"txt","len":0},{"id":"8007","post_id":"7868","mon_id":"1159278","chapter_id":"1159328","question":"<p>Vi\u1ebft t\u1ec9 s\u1ed1 l\u01b0\u1ee3ng gi&aacute;c g&oacute;c cos 61&deg;&nbsp;th&agrave;nh t\u1ec9 s\u1ed1 l\u01b0\u1ee3ng gi&aacute;c&nbsp;c\u1ee7a g&oacute;c nh\u1ecf h\u01a1n 45&deg; ta \u0111\u01b0\u1ee3c:<\/p>","options":["<strong>A.<\/strong> cot 29&deg;","<strong>B.<\/strong> sin 29&deg;","<strong>C.<\/strong> &ndash;sin 29&deg;","<strong>D.<\/strong> tan 29&deg;"],"correct":"2","level":"2","hint":"","answer":"<p>Ch\u1ecdn&nbsp;<span style=\"color:#27ae60;\"><\/span><span style=\"color:#16a085;\"><strong>B.<\/strong>&nbsp;sin 29&deg;<\/span><\/p><p>N\u1ebfu hai g&oacute;c ph\u1ee5 nhau th&igrave; sin g&oacute;c n&agrave;y b\u1eb1ng cos g&oacute;c kia n&ecirc;n&nbsp;<span style=\"color:#16a085;\"><strong>cos 61&deg; = sin (90&deg; &ndash; 61&deg;) = sin 29&deg;<\/strong><\/span>.<\/p>","type":"choose","extra_type":"classic","time":"0","user_id":"127","test":"0","date":"2024-10-21 02:27:29","option_type":"txt","len":2},{"id":"8008","post_id":"7868","mon_id":"1159278","chapter_id":"1159328","question":"<p>Vi\u1ebft t\u1ec9 s\u1ed1 l\u01b0\u1ee3ng gi&aacute;c g&oacute;c cot 36&deg; th&agrave;nh t\u1ec9 s\u1ed1 l\u01b0\u1ee3ng gi&aacute;c&nbsp;c\u1ee7a g&oacute;c l\u1edbn h\u01a1n 45&deg; ta \u0111\u01b0\u1ee3c:<\/p>","options":["<strong>A.<\/strong> tan 54&deg;","<strong>B.<\/strong> sin 54&deg;","<strong>C.<\/strong> cos 54&deg;","<strong>D.<\/strong> &ndash;tan 54&deg;"],"correct":"1","level":"2","hint":"","answer":"<p>Ch\u1ecdn&nbsp;<span style=\"color:#16a085;\"><strong>A.<\/strong>&nbsp;tan 54&deg;<\/span><\/p><p>N\u1ebfu hai g&oacute;c ph\u1ee5 nhau th&igrave; tan g&oacute;c n&agrave;y b\u1eb1ng cot g&oacute;c kia n&ecirc;n:&nbsp;<span class=\"math-tex\">$\\cot36^0=\\tan(90^0-36^0)=\\tan54^0$<\/span>.<\/p>","type":"choose","extra_type":"shape1","time":"0","user_id":"127","test":"0","date":"2024-10-21 02:29:24","option_type":"txt","len":0}]}