How can a right triangle with three sides know how to find three angles? For example, how can a right triangle with three sides of 3, 4, and 5 find its angle according to the change?

How can a right triangle with three sides know how to find three angles? For example, how can a right triangle with three sides of 3, 4, and 5 find its angle according to the change?

First of all, let's look at the relationship between the three sides. It's very easy to compare the size of the three corners. Just compare the length of the sides
Then we need to see if there is an obvious right side which is half of the hypotenuse. If so, the angle of the right side must be 30 degrees. (right triangle)
In addition to the above case and isosceles right triangle case, we can only use trigonometric function as mentioned above to convert sin, cos, etc. into angle