Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
Xét tam giác ABC có A = 180 - C - B =180 - 120 - 30 = 30
Vì AE là phân giác góc ngoài tại A
=> BAE = ( 180 - A ) / 2 = ( 180 - 30 ) / 2 = 75
Có ABE + ABC = 180
=> ABE = 180 - ABC = 180 - 120 = 60
Xét tam giác AEB có BEA + BAE + ABE = 180
=> AEB = 180 - 60 -75 = 45
Vậy AEB = 45
ta có tam giác abc cân tại a có số đo là 100 độ
=> B =C = (180-100)/2 = 40 độ
vì hai đường phân giác của hai góc B và C trong tam giác abc cắt nhau tại i
=> CBI= BCI= 40/2 = 20 độ
vì tổng số đo các góc trong tam giác = 180 độ
=> BIC = 180 - CBI-BIC= 180 -(20+20) = 140 (độ)
Ta có: \(\frac{x-y}{3}=\frac{x+y}{13}=\frac{x-y+x+y}{16}=\frac{2x}{16}=\frac{x}{8}=\frac{25x}{200}=\frac{xy}{200}\)
Suy ra: \(25x=xy\Rightarrow y=25\)
Ta có: \(\frac{x-y}{3}=\frac{x+y}{13}\)
Suy ra: \(13x-13y=3x+3y\)
Thế y vào đẳng thức trên:
\(13x-325=3x+75\)
Suy ra: \(10x=325+75=400\Rightarrow x=40\)
Vậy ........
treuyrht5tttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttt
Xét tam giác BIC có : BIC + IBC + ICB = 180
=> IBC + ICB = 180 - 120 = 60
Vì BI và CI là phân giác góc ABC và góc ACB
=> IBC + ICB = ( ABC + ACB) / 2
=> ABC + ACB = 2 ( IBC + ICB ) = 60 x 2 = 120
=> A = 180 - ( ACB + ABC ) = 180 - 120 = 60
Vậy A = 60