Relation des sinus Caractérisation des quadrilatères convexes

ABC
a
sinA =b sinB =c sinC = 2R
a=BC, b =CA, c =AB, R =A, B, C
ABC
ABCD
\
(−→ CA, −−→ CB) =
\
(−−→ DA, −−→ DB) + π2π
ABCDEF ABCD E = (AB)∩
(CD), F = (BC)∩(AD)
ADE, ABF, BCE, CDF
ABC A0B0C0
ABC
A0B0C0

ABC
P Q R BC CA AB
P Q +QR +RP
ABC
P QR
Q R P P Q +P R
P Q R
ABC

P R f =sAB ◦sCA ◦sBC
BC CA AB f
P Q R A B C
ABC P1P2P AB AC
P1R Q P2P QR
P1P2AP A
ABC

P QR
ABC

P QR
ABC
ABC
ABC
AP A A
ABC