Some conclusions: The following are all vectors.
1 if p is the center of gravity of △ABC, PA+PB+PC=0.
2 if p is PA of △ABC? PB=PB? PC=PA? PC (internal product)
3 If p is the inner APA+BP B+CPC of △ABC = 0 (ABC is trilateral).
4 If P is the outer center of △ABC |PA|? =|PB|? =|PC|?
(AP means AP vector |AP| is its module)
5 AP=λ(AB/|AB|+AC/|AC|), λ∈[0, +∞) then the straight line AP passes through the heart of △ABC.
6 AP = λ (AB/| AB | COSB+AC/| AC | COSC), λ ∈ [0, +∞) passes through the center of gravity.
7 AP=λ(AB/|AB|sinB+AC/|AC|sinC),λ∈[0,+∞)
Or AP=λ(AB+AC), λ∈[0, +∞) passes through the center of gravity.
8. If aOA=bOB+cOC, then 0 is the intersection of the centroid of ∠A and the bisector of ∠ B and C.
The following is the relevant proof of some conclusions.
1.
O is the interior of a triangle if and only if aOA vector +bOB vector +cOC vector =0 vector.
Adequacy:
Known aOA vector +bOB vector +cOC vector =0 vector,
AcCOrding to vector addition, the co intersection AB is extended to d:
OA=OD+DA, OB=OD+DB, substituting for known:
a(OD+DA)+b(OD+DB) +cOC=0,
Because of the connection between OD and OC***, OD=kOC can be set.
The above formula can be replaced by a vector of (ka+kb+c) OC+( aDA+bDB)=0.
Vector DA and DB*** lines, vector OC and vectors DA and DB are not * * * lines,
So there can only be: ka+kb+c=0, aDA+bDB=0 vectors,
According to the vector of aDA+bDB=0, the ratio of the length of DA to DB is b/a,
So CD is the bisector of ∠ACB, which proves that the other two are also angular bisectors.
Necessity:
As we all know, O is the center of a triangle.
Let BO and AC intersect at e, and CO and AB intersect at f,
O is the heart
∴b/a=AF/BF,c/a=AE/CE
The parallel lines passing through a as CO intersect with the extension line of B0 at n, and the parallel lines passing through a as BO intersect with the extension line of c0 at m,
So the quadrilateral Oman is a parallelogram.
According to the parallelogram law, it is concluded that
Vector OA
= vector OM+ vector ON
=(OM/CO)* vector CO+(ON/BO)* vector BO
=(AE/CE)* Vector CO+(AF/BF)* Vector BO
=(c/a)* vector CO+(b/a)* vector BO∴a* vector OA=b* vector BO+c* vector CO.
∴a* vector OA+b* vector OB+c* vector OC= vector 0.
2.
It is known that △ABC is an oblique triangle, O is a fixed point on the plane where △ABC lies, and the moving point P satisfies the vector OP = OA+ENTER {(AB/| AB | 2 * SIN2B)+AC/(| AC | 2 * SIN2C)}.
Find the vertical center of the locus of point P passing through the triangle.
OP = OA+enter {(ab/| ab | 2 * sin2b)+AC/(| AC | 2 * sin2c)},
OP-OA = enter {(ab/| ab | 2 * sin2b)+AC/(| AC | 2 * sin2c)},
AP = enter {(ab/| ab | 2 * sin2b)+AC/(| AC | 2 * sin2c)},
AP? BC= enter {(AB? BC/| AB | 2 * SIN2B)+AC? BC/(| AC | 2 * sin2c)},
AP? BC= enter {|AB|? | BC | cos( 180-b)/(|ab|^2*sin2b)+| AC |? | BCE | COSC/(| AC | 2 * SIN2C)},
AP? BC= enter {-|AB|? | BC | cos b/(|ab|^2*2sinb cos b)+| AC |? |BC| cosC/(|AC|^2*2sinC cosC)},
AP? BC = enter {-| BC |/(| AB | * 2 sinb)+| BC |/(| AC | * 2 sinc)},
According to sine theorem: |AB|/sinC=|AC|/ sinB, so |AB|*sinB=|AC|*sinC.
∴-|bc|/(| ab | * 2 sinb)+| BC |/(| AC | * 2 sinc)= 0,
Is that AP? BC=0,
The locus of point P passes through the vertical center of the triangle.
3.
OP = OA+λ(AB/(| AB | sinB)+AC/(| AC | sinC))
OP-OA =λ(AB/(| AB | sinB)+AC/(| AC | sinC))
AP =λ(AB/(| AB | sinB)+AC/(| AC | sinC))
AP and AB/|AB|sinB+AC/|AC|sinC***
According to sine theorem: |AB|/sinC=|AC|/sinB,
So |AB|sinB=|AC|sinC,
So AP and AB+AC***
AB+AC passes through the midpoint D of BC, so the trajectory of point P also passes through the midpoint D,
Point p passes through the center of gravity of the triangle.
4.
OP = OA+λ(ABC OSC/| AB |+ACcosB/| AC |)
OP = OA+λ(ABC OSC/| AB |+ACcosB/| AC |)
AP=λ(ABcosC/|AB|+ACcosB/|AC|)
AP? BC=λ(AB? BC cosC/|AB|+AC? BC cosB/|AC|)
=λ([|AB|? | BC | cos( 180-B)cosC/| AB |+| AC |? |BC| cosC cosB/|AC|]
=λ[-|BC|cosBcosC+|BC| cosC cosB]
=0,
The vector AP is perpendicular to the vector BC,
The trajectory of point p is too vertical.
5.
OP=OA+λ(AB/|AB|+AC/|AC|)
OP=OA+λ(AB/|AB|+AC/|AC|)
OP-OA =λ(AB/|AB|+AC/|AC|)
AP=λ(AB/|AB|+AC/|AC|)
AB/|AB| and AC/|AC| are unit length vectors in AB and AC directions,
The sum vector of unit vectors of vectors AB and AC,
Because it is a unit vector, the module lengths are all equal, forming a diamond.
The sum vector of the unit vectors of vectors AB and AC is a rhombic diagonal,
It is easy to know that it is an angular bisector, so the trajectory of point P passes through the heart.