Y\u00eau c\u1ea7u c\u1ee7a c\u00e1c h\u00ecnh kh\u1ea3m l\u00e0 khi c\u00e1c \u0111\u01b0\u1eddng chu vi g\u1eb7p nhau t\u1ed5ng c\u00e1c g\u00f3c ph\u1ea3i b\u1eb1ng 360o, nh\u1edd v\u1eady khi gh\u00e9p ch\u00fang l\u1ea1i s\u1ebd kh\u00f4ng c\u00f3 khe h\u1edf. N\u1ebfu d\u00f9ng c\u00e1c m\u1ea3nh kh\u1ea3m g\u1ed3m c\u00e1c h\u00ecnh nhi\u1ec1u c\u1ea1nh th\u00ec c\u00f3 bao nhi\u00eau c\u00e1ch l\u1eafp gh\u00e9p? 1:Unb I<\/p>\n\n\n\n
Hlnh4<\/p>\n\n\n\n
lil nh 2<\/p>\n\n\n\n
1-linh] lfinh 6<\/p>\n\n\n\n
Hinh? Hinh8 l:linh9<\/p>\n\n\n\n
Hinh 10 1-linh II<\/p>\n\n\n\n
Hinh 12 Efinh 13<\/p>\n\n\n\n
Tr\u01b0\u1edbc h\u1ebft xem x\u00e9t t\u1eeb kh\u00eda c\u1ea1nh c\u00e1c \u0111i\u1ec3m g\u1eb7p nhau c\u1ee7a c\u00e1c h\u00ecnh c\u00f3 nhi\u1ec1u c\u1ea1nh. Do c\u00e1c g\u00f3c trong c\u1ee7a c\u00e1c \u0111a gi\u00e1c nh\u1ecf nh\u1ea5t l\u00e0 60o, l\u1edbn nh\u1ea5t l\u00e0 180o n\u00ean ch\u1ec9 c\u00f3 c\u00e1c h\u00ecnh 3, 4, 5, 6 c\u1ea1nh l\u00e0 c\u00f3 th\u1ec3 s\u1eed d\u1ee5ng. Ta th\u1eed x\u00e9t ba t\u00ecnh hu\u1ed1ng. Ta g\u1ecdi c\u00e1c h\u00ecnh \u0111a gi\u00e1c c\u00f3 c\u00e1c s\u1ed1 c\u1ea1nh l\u00e0 x, y, z th\u00ec c\u00e1c g\u00f3c trong s\u1ebd l\u00e0:<\/p>\n\n\n\n
Khi gh\u00e9p ch\u00fang l\u1ea1i v\u1edbi nhau \u0111\u1ec3 kh\u1ea3m th\u00ec<\/p>\n\n\n\n
B\u1edfi v\u00ec 1\/x + 1\/y + 1\/z = 1\/2<\/p>\n\n\n\n
Kh\u00f4ng k\u1ec3 tr\u1eadt t\u1ef1 s\u1eafp x\u1ebfp c\u1ee7a c\u00e1c s\u1ed1 x, y, z th\u00ec ph\u01b0\u01a1ng tr\u00ecnh n\u00e0y c\u00f3 10 nh\u00f3m nghi\u1ec7m l\u00e0: (3, 7, 42); (3, 8, 24); (3, 9, 18); (3, 10, 15); (3, 12, 12); (4, 5, 20); (4, 6, 12); (4, 8, 8); (5, 5, 10); (6, 6, 6).<\/p>\n\n\n\n
C\u0169ng v\u1edbi l\u00ed lu\u1eadn t\u01b0\u01a1ng t\u1ef1 khi ch\u1ecdn ph\u01b0\u01a1ng \u00e1n b\u1ed1n lo\u1ea1i \u0111a gi\u00e1c ta c\u00f3 b\u1ed1n nh\u00f3m nghi\u1ec7m: (3, 3, 4, 12); (3, 3, 6, 6); (3, 4, 4, 6); (4, 4, 4, 4).<\/p>\n\n\n\n
V\u1edbi ph\u01b0\u01a1ng \u00e1n n\u0103m lo\u1ea1i \u0111a gi\u00e1c s\u1ebd c\u00f3 hai nh\u00f3m nghi\u1ec7m (3, 3, 3, 3, 6) v\u00e0 (3, 3, 3, 4, 4), c\u00f2n n\u1ebfu d\u00f9ng s\u00e1u lo\u1ea1i \u0111a gi\u00e1c th\u00ec ch\u1ec9 c\u00f3 m\u1ed9t nh\u00f3m nghi\u1ec7m (3, 3, 3, 3, 3, 3).<\/p>\n\n\n\n
Nh\u01b0 v\u1eady n\u1ebfu x\u00e9t theo quan \u0111i\u1ec3m, \u0111i\u1ec3m giao nhau c\u1ee7a c\u00e1c \u0111a gi\u00e1c \u0111\u1ec1u c\u00f3 17 lo\u1ea1i c\u00e1ch ph\u1ed1i tr\u00ed kh\u00e1c nhau. Th\u1ebf nh\u01b0ng c\u00f3 ph\u1ea3i c\u1ea3 17 ph\u01b0\u01a1ng \u00e1n n\u00e0y \u0111\u1ec1u c\u00f3 th\u1ec3 s\u1eed d\u1ee5ng trong k\u0129 thu\u1eadt n\u1ea1m kh\u1ea3m. Th\u1ef1c t\u1ebf ch\u1ec9 c\u00f3 c\u00e1c \u0111a gi\u00e1c \u0111\u1ec1u c\u00f3 3, 4, 6, 8, 12 c\u1ea1nh l\u00e0 c\u00f3 th\u1ec3 gh\u00e9p n\u1ed1i v\u00e0o nhau \u0111\u1ec3 kh\u1ea3m l\u00e0m 11 lo\u1ea1i kh\u1ea3m gh\u00e9p \u0111\u1ec3 l\u1ea5p k\u00edn b\u1ec1 m\u1eb7t m\u00e0 kh\u00f4ng c\u00f3 khe h\u1edf, c\u00f2n s\u00e1u lo\u1ea1i \u0111a gi\u00e1c kh\u00e1c ch\u01b0a t\u00ecm \u0111\u01b0\u1ee3c c\u00e1ch gh\u00e9p th\u00e0nh c\u00f4ng.<\/p>\n\n\n\n
Th\u1ebf th\u00ec t\u1eeb 11 lo\u1ea1i t\u00ecnh hu\u1ed1ng c\u00f3 th\u1ec3 c\u00f3 c\u00e1ch s\u1eafp x\u1ebfp n\u00e0o? Ch\u00fang ta c\u00f3 th\u1ec3 b\u00e0n \u0111\u1ebfn b\u1ed1n lo\u1ea1i s\u1eafp x\u1ebfp ch\u00ednh:<\/p>\n\n\n\n
C\u00e1c h\u00ecnh kh\u1ea3m \u0111\u1ec1u: T\u1ee9c l\u00e0 d\u00f9ng c\u00e1ch l\u1eafp gh\u00e9p c\u00e1c \u0111a gi\u00e1c c\u00f9ng lo\u1ea1i nh\u01b0 \u1edf c\u00e1c h\u00ecnh v\u1ebd 1 – 3. Ch\u1ec9 c\u00f3 3 lo\u1ea1i l\u1eafp gh\u00e9p (6, 6, 6); (4, 4, 4, 4) v\u00e0 (3, 3, 3, 3, 3).<\/p>\n\n\n\n
C\u00e1c h\u00ecnh kh\u1ea3m n\u1eeda \u0111\u1ec1u: D\u00f9ng c\u00e1ch l\u1eafp gh\u00e9p c\u00e1c h\u00ecnh \u0111a gi\u00e1c kh\u00f4ng \u0111\u1ed3ng nh\u1ea5t nh\u01b0ng s\u1ed1 \u0111i\u1ec3m giao nhau c\u1ee7a \u0111\u01b0\u1eddng bi\u00ean c\u00e1c \u0111a gi\u00e1c \u0111\u1ec1u gi\u1ed1ng nhau nh\u01b0 \u1edf c\u00e1c h\u00ecnh v\u1ebd t\u1eeb 4 – 9. C\u00f3 6 lo\u1ea1i (3, 12, 12); (4, 8, 8); (3, 3, 6, 6); (3, 4, 4, 6); (3, 3, 3, 6) v\u00e0 (3, 3, 3, 4, 4).<\/p>\n\n\n\n
C\u00e1c h\u00ecnh kh\u1ea3m \u0111\u1ec1u \u0111\u1eb7n: S\u1ed1 giao \u0111i\u1ec3m c\u1ee7a c\u00e1c \u0111\u01b0\u1eddng bi\u00ean c\u00e1c \u0111a gi\u00e1c l\u00e0 gi\u1ed1ng nhau, ch\u1ec9 c\u00f3 th\u1ee9 t\u1ef1 s\u1eafp x\u1ebfp kh\u00e1c nhau nh\u01b0 \u1edf c\u00e1c h\u00ecnh v\u1ebd 10 – 13. Lo\u1ea1i kh\u1ea3m n\u00e0y d\u1ef1a v\u00e0o giao \u0111i\u1ec3m c\u00e1c \u0111\u01b0\u1eddng bi\u00ean c\u1ee7a c\u00e1c \u0111a gi\u00e1c theo m\u1ed9t th\u1ee9 t\u1ef1 nh\u1ea5t \u0111\u1ecbnh, nh\u01b0ng v\u1ecb tr\u00ed t\u01b0\u01a1ng \u0111\u1ed1i c\u1ee7a c\u00e1c giao \u0111i\u1ec3m l\u00e0 v\u00f4 h\u1ea1n. V\u00ed d\u1ee5 n\u1ebfu d\u1ecbch chuy\u1ec3n \u00f4 gi\u1eefa c\u1ee7a h\u00ecnh 11 sang b\u00ean ph\u1ea3i m\u1ed9t \u00f4 ta s\u1ebd c\u00f3 m\u1ed9t lo\u1ea1i \u0111\u1ed3 h\u00ecnh kh\u1ea3m kh\u00e1c. N\u1ebfu c\u00e1ch 1, 2, 3\u2026 h\u00e0ng di chuy\u1ec3n sang ph\u1ea3i m\u1ed9t \u00f4 s\u1ebd \u0111\u01b0\u1ee3c m\u1ed9t h\u00ecnh kh\u1ea3m kh\u00e1c. V\u00ec v\u1eady \u1edf h\u00ecnh kh\u1ea3m n\u00e0y ta s\u1ebd thu \u0111\u01b0\u1ee3c nhi\u1ec1u lo\u1ea1i.<\/p>\n\n\n\n
C\u00e1c h\u00ecnh kh\u1ea3m kh\u00f4ng \u0111\u1ec1u \u0111\u1eb7n: C\u00e1c giao \u0111i\u1ec3m c\u1ee7a c\u00e1c \u0111\u01b0\u1eddng bi\u00ean c\u1ee7a c\u00e1c \u0111a gi\u00e1c kh\u00f4ng gi\u1ed1ng nhau, s\u1ed1 giao \u0111i\u1ec3m c\u0169ng kh\u00f4ng gi\u1ed1ng nhau. C\u00e1c h\u00ecnh kh\u1ea3m n\u00e0y c\u0169ng c\u00f3 v\u00f4 s\u1ed1 lo\u1ea1i.<\/p>\n\n\n\n
Ngo\u00e0i c\u00e1c ph\u01b0\u01a1ng \u00e1n k\u1ec3 tr\u00ean ng\u01b0\u1eddi ta c\u00f3 th\u1ec3 s\u1eed d\u1ee5ng c\u00e1c h\u00ecnh tam gi\u00e1c, h\u00ecnh b\u1ed1n c\u1ea1nh kh\u00f4ng \u0111\u1ec1u ho\u1eb7c c\u00e1c \u0111\u01b0\u1eddng g\u1ea5p kh\u00fac, c\u0169ng nh\u1eadn \u0111\u01b0\u1ee3c c\u00e1c h\u00ecnh kh\u1ea3m tinh x\u1ea3o.<\/p>\n\n\n\n
T\u1eeb kho\u00e1: H\u00ecnh kh\u1ea3m; H\u00ecnh \u0111a gi\u00e1c \u0111\u1ec1u.<\/p>\n\n\n\n
<\/p>\n\n\n\n\n\n\n","protected":false},"excerpt":{"rendered":"
Y\u00eau c\u1ea7u c\u1ee7a c\u00e1c h\u00ecnh kh\u1ea3m l\u00e0 khi c\u00e1c \u0111\u01b0\u1eddng chu vi g\u1eb7p nhau t\u1ed5ng c\u00e1c g\u00f3c ph\u1ea3i b\u1eb1ng 360o, nh\u1edd v\u1eady khi gh\u00e9p ch\u00fang l\u1ea1i s\u1ebd kh\u00f4ng c\u00f3 khe h\u1edf. N\u1ebfu d\u00f9ng c\u00e1c m\u1ea3nh kh\u1ea3m g\u1ed3m c\u00e1c h\u00ecnh nhi\u1ec1u c\u1ea1nh th\u00ec c\u00f3 bao nhi\u00eau c\u00e1ch l\u1eafp gh\u00e9p? 1:Unb I Hlnh4 lil nh 2 1-linh] […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":"","_disable_autopaging":false},"categories":[15,9],"tags":[],"class_list":["post-7547","post","type-post","status-publish","format-standard","hentry","category-hoi-dap-khoa-hoc","category-toan-hoc"],"_links":{"self":[{"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/posts\/7547","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/comments?post=7547"}],"version-history":[{"count":0,"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/posts\/7547\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/media?parent=7547"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/categories?post=7547"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/tags?post=7547"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}