proving angle relationships

Hello, smart_pirate!

Given: line ABBC;    1 and 3 are complementry.\displaystyle \text{Given: line }AB \perp BC;\;\;\angle 1\text{ and }\angle 3\text{ are complementry.}

Prove:   2=3\displaystyle \text{Prove: }\;\angle2 \:=\:\angle 3

Code:
      A
      *         E
      *       *
      *     *
      * 1 *
      * * 2
    B *  *  *  *  * C
         *  3
            *
               *
                  D

ABC=90o1+2=90o2=90o1\displaystyle \angle ABC = 90^o\quad\Rightarrow\quad \angle 1 + \angle2 \:=\:90^o \quad\Rightarrow\quad \angle 2 \:=\:90^o - \angle 1 .[1]

1 and 3 are complementary: 1+3=90o3=90o1\displaystyle \angle 1\text{ and }\angle3\text{ are complementary: }\angle 1 + \angle 3 \:=\:90^o \quad\Rightarrow\quad \angle 3 \:=\:90^o - \angle 1 .[2]

Equate [1] and [2]: . 2=3\displaystyle \angle 2 \:=\:\angle 3

 
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