Ta có:
Góc ABC + góc ACB = 90o
\(\Rightarrow\frac{1}{2}\)góc ABC + \(\frac{1}{2}\)góc ACB = \(\frac{1}{2}.90^o=45^o\)
\(\Rightarrow\)Góc IBC + góc ICB = 45o
Xét \(\Delta BIC\):
Góc IBC + góc ICB + góc BIC = 180o
(Góc IBC + góc ICB) + góc BIC = 180o
45o + góc BIC =180o
Góc BIC = 135o
Ta có: góc A + góc B + góc C = 1800
=> góc B + góc C = 180 - góc A = 180 - 90 = 900
\(\Rightarrow\frac{B_1+B_2}{2}+\frac{C_1+C_2}{2}=90^0\)
\(\Rightarrow\frac{2B_1}{2}+\frac{2C_1}{2}=90^0\Rightarrow B_1+C_1=90^0\)
Hay góc BIC = 900
Vậy góc BIC = 900
À tui nhầm
góc B + góc C = 900
=> B1 + B2 + C1 + C2 = 900
=> 2B1 + 2C1 = 900
=> 2(B1 + C1) = 900
=> B1 + C1 = 450
Có: góc BIC + B1 + C1 = 1800
=> góc BIC = 180 - 45 = 1350
Vậy góc BIC = 1350