{"common":{"save":0,"post_id":"7042","level":1,"total":10,"point":10,"point_extra":0},"segment":[{"id":"4786","post_id":"7042","mon_id":"1158924","chapter_id":"1159141","question":"<p>\u0110\u1ed5i s\u1ed1 \u0111o 80&deg; sang \u0111\u01a1n v\u1ecb radian ta \u0111\u01b0\u1ee3c:<\/p>","options":["<strong>A.<\/strong> <span class=\"math-tex\">$\\dfrac{80}{\\pi}$<\/span>","<strong>B.<\/strong> <span class=\"math-tex\">$\\dfrac{4}{9}$<\/span>","<strong>C.<\/strong> <span class=\"math-tex\">$\\dfrac{4}{9\\pi}$<\/span>","<strong>D.<\/strong> <span class=\"math-tex\">$\\dfrac{4\\pi}{9}$<\/span>"],"correct":"4","level":"1","hint":"","answer":"<p>Ch\u1ecdn&nbsp;<span style=\"color:#16a085;\"><strong>D.<\/strong>&nbsp;<span class=\"math-tex\">$\\dfrac{4\\pi}{9}$<\/span><\/span><\/p>","type":"choose","extra_type":"classic","user_id":"131","test":"0","date":"2023-11-20 03:38:02","option_type":"math","len":0},{"id":"4788","post_id":"7042","mon_id":"1158924","chapter_id":"1159141","question":"<p>T&iacute;nh \u0111\u1ed9 d&agrave;i c\u1ee7a cung tr&ecirc;n \u0111\u01b0\u1eddng&nbsp;tr&ograve;n c&oacute; b&aacute;n k&iacute;nh R = 20 cm v&agrave; s\u1ed1 \u0111o&nbsp;<span class=\"math-tex\">$\\alpha=\\dfrac{2\\pi}{5}$<\/span>.<\/p>","options":["<strong>A.<\/strong> 15,7 cm","<strong>B.<\/strong> 18,8 cm","<strong>C.<\/strong> 25,13 cm","<strong>D.<\/strong> 21,99 cm"],"correct":"3","level":"1","hint":"","answer":"<p>Ta c&oacute;:&nbsp;<span class=\"math-tex\">$l=R.\\alpha=20 . \\dfrac{2\\pi}{5}=8\\pi\\approx 25,13$<\/span>&nbsp;(cm)<\/p><p>Ch\u1ecdn&nbsp;<span style=\"color:#16a085;\"><strong>C.<\/strong> 25,13 cm<\/span><\/p>","type":"choose","extra_type":"shape1","user_id":"131","test":"0","date":"2023-11-20 03:41:05","option_type":"txt","len":0},{"id":"4789","post_id":"7042","mon_id":"1158924","chapter_id":"1159141","question":"<p>N\u1ebfu&nbsp;<span class=\"math-tex\">$cos\\space a=\\dfrac{3}{5}$<\/span>&nbsp;v&agrave;&nbsp;<span class=\"math-tex\">$cos\\space b=\\dfrac{-4}{5}$<\/span>&nbsp;th&igrave;&nbsp;<span class=\"math-tex\">$cos(a+b).cos(a-b)$<\/span>&nbsp;b\u1eb1ng&nbsp;<\/p>","options":["<strong>A.<\/strong> 0","<strong>B.<\/strong> 2","<strong>C.<\/strong> 4","<strong>D.<\/strong> 5"],"correct":"1","level":"1","hint":"","answer":"<p>Ta c&oacute;:&nbsp;<span class=\"math-tex\">$cos(a+b).cos(a-b)$<\/span>&nbsp;<\/p><p>=&nbsp;<span class=\"math-tex\">$\\dfrac{1}{2}\\bigg[cos(a+b+a-b)+cos(a+b-a+b)\\bigg]$<\/span><\/p><p>=&nbsp;<span class=\"math-tex\">$\\dfrac{1}{2}\\bigg[cos2a+cos2b\\bigg]$<\/span><\/p><p>=&nbsp;<span class=\"math-tex\">$\\dfrac{1}{2}\\bigg[2cos^2a-1+2cos^2b-1\\bigg]$<\/span><\/p><p>=&nbsp;<span class=\"math-tex\">$\\dfrac{1}{2}\\bigg[2.\\dfrac{9}{25}-1+2.\\dfrac{16}{25}-1\\bigg]$<\/span><\/p><p>= 0<\/p><p>Ch\u1ecdn&nbsp;<span style=\"color:#16a085;\"><strong>A.<\/strong> 0<\/span><\/p>","type":"choose","extra_type":"shape1","user_id":"131","test":"0","date":"2023-11-20 03:47:55","option_type":"txt","len":0}]}