a) tam giac PQR co goc Q+ goc R + goc QPR = 180 do
=> goc QPR = 180 do- 80 do - 40 do= 60 do
b) PI la p/g goc QPR (gt)
=> goc QPI= goc RPI = goc QPR /2= 60 do/2= 30 do
tam giac QIP co goc HIP + goc Q + goc QPI = 180 do
=> goc HIP= 180 do - 80 do - 30 do = 70 do
c) tam gic HIP co PHI +HIP + HPI = 180 do
=> HPI = 180 -90 -70 = 20 do