(1) First prove that △ABC is a right triangle with ∠ACB as the right angle;
(2) Make symmetrical figures and calculate the area of △ABC.
Detailed answer:
(1) Intercept AD=AC on line AB
AB = 2AC,AD=AC
∴ DB=DC
∴ ∠ABC=∠DCB
AD = AC, and the angle between ad and AC ∠ BAC = 60.
△ ADC is an equilateral triangle.
∴ ∠ADC = 60
∫∠ADC is the external angle of isosceles △DBC.
∴∠ADC = ∠ABC + ∠DCB
= 2∠ABC
60 = 2 ∠ ABC
∴ ∠ABC = 30
And < BAC = 60.
∴, ∠ ACB = 90 in △ABC.
(2) Make the symmetry point of point P about AC P 1,
Make the symmetric point P2 of point P about AB,
Make P3, the symmetry point of P about BC,
Even AP 1, AP2 and P 1P2 are known from symmetry:
△AP 1P2 is an isosceles triangle, AP 1 = AP2 = √3, P 1P2 = 3, ∠ p 1ap2 = 2 ∠ BAC = 120.
It is easy to find the area of isosceles △P 1AP2: S△P 1AP2 = (3√3)/ 4.
Similarly, △BP2P3 is an equilateral triangle, BP2 = BP3 = P2P3 = 5, ∠ p2bp3 = 2 ∠ ABC = 60.
It is easy to find the area of equilateral △BP2P3: S△BP2P3 = (25√3)/ 4.
Even CP 1 even CP3,
Then CP 1 = CP = 2, CP3 = CP = 2, ∠ P 1cp3 = 2 ∠ ACB = 180, that is, lines P 1, C and P3 * *.
In △P 1P2P3,P 1P2 = 3,P 1P3 = 4,P2P3 = 5。
∴ △P 1P2P3 is Rt△, and its area is: S Rt△P 1P2P3 = 6.
∴s△p 1ap2+s△bp2p 3+s rt△p 1p2p 3
=(3√3)/ 4 +(25√3)/ 4 + 6
= 7√3 + 6
According to symmetry:
S△AP2B = S△APB
S△BP3C = S△BPC
S△AP 1C = S△APC
∴ S△APB + S△BPC + S△APC
=( 1/2)×(S△p 1ap 2+S△bp2p 3+S Rt△p 1p2p 3)
= ( 1/2)× (7√3 + 6)
= (7√3 + 6)/ 2
That is, the area of △ABC is (7√3+6)/ 2.