標題:
數學大難題
發問:
7.在圖中，AB=BD=DF=7cm，FG=24cm及BC//DE//FG a.求DP和DE的長度 b.由此，求BC的長度 圖：(&b=2&(這個位係冇;的)f=190113) http://www.wretch.cc/album/show.php?i=Puchikoyiu&b=2&f=1901133632&p=5 （係下面果張）↑ ８．sin2次+sin2次18度 ９．tan15度xtan75度+sin15度/cos75度 請各大大幫助求求小的,感激不盡! 更新: 7.圖: http://s78.photobucket.com/albums/j107/puchikoyiu/?action=view¤t=0002.jpg 8.sin2次72度+sin2次18度
最佳解答:
7a)Consider triangle BFG. BP/PG = BD/DF = 1 (intercept theorem) BP=PG So, DP = 1/2FG = 12 cm,Ans.(mid-pt. theorem) b)Consider triangle BCG. BP/PG = CE/EG = BD/DF = 1 (intercept theorem) BP=PG and CE=EG So, PE=1/2 BC Consider triangle ADE. DE = 2BC (mid-pt. theorem) DP + PE = 2BC 12 + 1/2BC = 2BC BC = 12/ (3/2) = 8 cm,Ans. 但係要先找DE的長度來計我就唔識喇... 8) sin^2 72 + sin^2 18 = sin^2 (90 - 18) + sin^2 18 = cos^2 18 + sin^2 18 =1,Ans. 9) tan15 x tan75 +sin15/cos75 =tan15 x tan(90 - 15) + sin15/cos(90 - 15) = tan15/tan15 + sin15/sin15 =2,Ans.
其他解答:
數學大難題
發問:
7.在圖中，AB=BD=DF=7cm，FG=24cm及BC//DE//FG a.求DP和DE的長度 b.由此，求BC的長度 圖：(&b=2&(這個位係冇;的)f=190113) http://www.wretch.cc/album/show.php?i=Puchikoyiu&b=2&f=1901133632&p=5 （係下面果張）↑ ８．sin2次+sin2次18度 ９．tan15度xtan75度+sin15度/cos75度 請各大大幫助求求小的,感激不盡! 更新: 7.圖: http://s78.photobucket.com/albums/j107/puchikoyiu/?action=view¤t=0002.jpg 8.sin2次72度+sin2次18度
最佳解答:
7a)Consider triangle BFG. BP/PG = BD/DF = 1 (intercept theorem) BP=PG So, DP = 1/2FG = 12 cm,Ans.(mid-pt. theorem) b)Consider triangle BCG. BP/PG = CE/EG = BD/DF = 1 (intercept theorem) BP=PG and CE=EG So, PE=1/2 BC Consider triangle ADE. DE = 2BC (mid-pt. theorem) DP + PE = 2BC 12 + 1/2BC = 2BC BC = 12/ (3/2) = 8 cm,Ans. 但係要先找DE的長度來計我就唔識喇... 8) sin^2 72 + sin^2 18 = sin^2 (90 - 18) + sin^2 18 = cos^2 18 + sin^2 18 =1,Ans. 9) tan15 x tan75 +sin15/cos75 =tan15 x tan(90 - 15) + sin15/cos(90 - 15) = tan15/tan15 + sin15/sin15 =2,Ans.
其他解答:
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7.無法看圖 8.sin2次(呢度係咪仲有ga?)+sin2次18度,未見過甘ge題. 9. tan15度xtan75度+sin15度/cos75度 =tan15x(1/tan15)+sin15/sin15 =1+1 =2 (so easy!)|||||呢個....你果個網都開唔到....冇圖唔識計...= =
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