18. AN IDEA FOR PROVING PROBLEMS IS FORROWING:

At proving problems, you must have a different approach. Because you already find answers. All your job is connecting between assumptions and conclusion. Not only calculating. So, I suggest follwing:

(1) Clear your GOAL(=conclusion) by underlining in wavy.
(2) Clear your STARTING POINTS(=assumptions) by underlining in straight.
(3) Think about the LAST STEP for your GOAL. This is important.
(4) Make a note about the things useful for solving. For example, formulas, theorems, definitions, mathematical property and so on.
Solve them like a maze.

Here is a sample question.

When you see this, act like follows. Let’s underline.

Next, think “What is the last step for goal?” It’s difficult a little. The last step is proving that this triangle is isosceles. Based on the edge AB, prove this is isosceles. (I omit these steps. Think, please.) Then you can get CA=BC. In a similar way, based on the edge BC, you can get also CA=AB. Therefore AB=BC=CA, and we can say this triangle ABC is equilateral. This is goal.

See you next.

Nasuno Kumao