2. It can be written directly in the Rt triangle and pasted at the back (due to the vertical relationship), which is the most standard. And trigonometric functions and Pythagoras can be used after this writing.

3, you say that the coordinates of a and b are substituted into the original function to get:

4. no need.

As long as the key steps are met and the conclusion is correct, you can get full marks. Don't worry too much. The steps should not be too complicated, and some obvious steps should not be written. Let's go I recommend a problem-solving website to you, hoping it will help you. There are exercises in all subjects in junior high school. Come on!