Câu hỏi của Hiếu Nguyễn Thị

Question

HT.Phong (9A5) · Accepted Answer

Xét ΔABE có: $\widehat{BAE}+\widehat{ABE}+\widehat{AEB}=180^o$

$\Rightarrow90^o+x+x=180^o\Rightarrow2x=180^o-90^o=90^o$

$\Rightarrow x=\dfrac{90^o}{2}=45^o$

Xét ΔABC có: $\widehat{ABC}+\widehat{BAC}+\widehat{CAB}=180^o$

$\Rightarrow\left(x+y\right)+90^o+30^o=180^o$

$\Rightarrow\left(x+y\right)+120^o=180^o$

$\Rightarrow45^o+y=180^o-120^o$

$\Rightarrow45^o+y=60^o$

$\Rightarrow y=60^o-45^o=15^o$

Câu trả lời:

Xét ΔABE có: $\widehat{BAE}+\widehat{ABE}+\widehat{AEB}=180^o$

$\Rightarrow90^o+x+x=180^o\Rightarrow2x=180^o-90^o=90^o$

$\Rightarrow x=\dfrac{90^o}{2}=45^o$

Xét ΔABC có: $\widehat{ABC}+\widehat{BAC}+\widehat{CAB}=180^o$

$\Rightarrow\left(x+y\right)+90^o+30^o=180^o$

$\Rightarrow\left(x+y\right)+120^o=180^o$

$\Rightarrow45^o+y=180^o-120^o$

$\Rightarrow45^o+y=60^o$

$\Rightarrow y=60^o-45^o=15^o$

Kiều Vũ Linh · Answer

∆ABE vuông tại A (gt)

⇒ ∠ABE + ∠AEB = 90⁰

⇒ x + x = 90⁰

⇒ x = 90⁰ : 2

= 45⁰

∆ABC vuông tại A (gt)

⇒ ∠ABC + ∠ACB = 90⁰

⇒ ∠ABC = 90⁰ - ∠ACB

= 90⁰ - 30⁰

= 60⁰

⇒ y = ∠ABC - x

= 60⁰ - 45⁰

= 15⁰