将一块直角三角板DEF放置在锐角△ABC上,使得该三角板的两条直角边DE、DF恰好分别经过点B、C.
(1)如图①,若∠A=40°时,点D在△ABC内,则∠ABC+∠ACB= 度,∠DBC+∠DCB= 度,∠ABD+∠ACD= 度;
(2)如图②,改变直角三角板DEF的位置,使点D在△ABC内,请探究∠ABD+∠ACD与∠A之间存在怎样的数量关系,并验证你的结论.
(3)如图③,改变直角三角板DEF的位置,使点D在△ABC外,且在AB边的左侧,直接写出∠ABD、∠ACD、∠A三者之间存在的数量关系.
![](https://img.xkw.com/dksih/QBM/editorImg/2023/6/19/a28767ef-3348-4a9d-a94c-5fc04884e4fb.png?resizew=523)
(1)如图①,若∠A=40°时,点D在△ABC内,则∠ABC+∠ACB= 度,∠DBC+∠DCB= 度,∠ABD+∠ACD= 度;
(2)如图②,改变直角三角板DEF的位置,使点D在△ABC内,请探究∠ABD+∠ACD与∠A之间存在怎样的数量关系,并验证你的结论.
(3)如图③,改变直角三角板DEF的位置,使点D在△ABC外,且在AB边的左侧,直接写出∠ABD、∠ACD、∠A三者之间存在的数量关系.
更新时间:2020-01-20 11:48:10
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