Classification of quadrilaterals.(We say yes for Isomorphism)
Convex quadrilateral ABCD:
<A + <B +<C +<D = 360, 0< <A,<B,<C,<D < 180
1)<A=<B=<C=<D=90 2)<A=<C=90,<B>90,<D<90(or<D>90,<B<90) 3)<A=<B=90,<C>90,<D<90 (or<C<90,<D>90) 4)<A=90,<B>90,<C>90,<D<90 5)<A=90,<B>90,<C<90,<D>90(or omit) 6)<A,B,C>90,<D<90,7)<A>90,<B,C,D<90.
Concave quadrilateral ABCD:
<A+<B+<C+<D=360, 0< <A,<B,<C,<D <360
1) <A>180,<B>90,<C,<D <90 2)<A>180,<C>90,<B,<D<90 3)<A>180,<B=90,<C,<D,<90 4)<A>180,<C=90,<B,<D <90 5)<A>180,<B,C,D <90.
I wrote this is the same as last one, but a little clearly.I wish it is right.
It is not good that I can't copy any words as usual.I can't save time.
