Question

the figure is a triangle.
what is the first step of indirectly proving this statement?

Answer 1

help me please!

Answer 2

If the figure is not a triangle, X would follow, however, X leads to contradiction. Therefore, the figure is a triangle.

Answer 3

Up to you to find a predicate X.

Answer 4

so the answer is the figure is a triangle?

Answer 5

You asked for the indirect way of proving somethings : it is structured as follow : Suppose X is false, then Y. But Y is false : therefore X is true.
The direct way is structured as follow : X is true if Y is true. Y is true. X is true.

For your case :
direct way : This is a triangle if <something>. <something> is true for the figure. Therefore, the figure is a triangle.
indirect way : If the figure is not a triangle, <something> would be true. However, we can see that <something> is false. Therefore, the figure is a triangle.

Answer 6

^^^ thats confusing.....