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發問:

1In the figure, AED and CDB are straight lines.Angle CAD = angle BED and angle CED = angle BED.1a.Prove triangle AEC is congruent to traingle AEB.1b.Show that angle EDC =... 顯示更多 1In the figure, AED and CDB are straight lines.Angle CAD = angle BED and angle CED = angle BED. 1a.Prove triangle AEC is congruent to traingle AEB. 1b.Show that angle EDC = 90度. 圖:http://hk.myblog.yahoo.com/Felix-Wong9426/photo?pid=4&fid=2 -------------------------------------------------------------------------------------------------------

最佳解答:

你係咪打錯左？ 因為 ext.∠ of△既關係， ∠CAD無可能=∠BED 如果你既問題係 In the figure, AED and CDB are straight lines.∠CAD=∠BAD and ∠CED=∠BED 就咁計： 1a)∠CEA=180°-∠CED(adj.∠on st. line) ∠BEA=180°-∠BED(adj.∠on st. line) ∵∠CED=∠BED(given) ∴∠CEA=∠BEA ∠ACE=180°-∠CEA-∠CAD(∠sum of △) ∠ABE=180°-∠BEA-∠BAD(∠sum of △) ∵∠CAD=∠BAD(given) ∴∠ACE=∠ABE △AEC=△AEB(AAA) 1b)∵△AEC=△AEB(proved) and AED is a straight line ∴∠EDC=∠EDB ∠EDC+∠EDB=180°(adj.∠on st. line) 2∠EDC=180° ∠EDC=90°

其他解答:

1a.Prove triangle AEC is congruent to traingle AEB 似乎條式錯左 如(angle CAD = angle BED)根本冇關係 應該係angleCAD=angleBAD 可以咁計 because angleCAD=angleBAD angle CED = angle BED 180-angleCED=angleAEC=180-angle BED=angleAEB AE=AE(common side) therefore triangle AEC is congruent to traingle AEB(A.S.A.)(Angle Side Angle) 1b.Show that angle EDC = 90度呢條可以咁計 because triangle AEC is congruent to traingle AEB,and CDB is a straight line therefore angleCDA=angleADB 180/2=90 therefore angleEDC = 90