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Eight Answers to Mathematics in Beijing Normal University
1. If the waist length is x, the midline of the base of an isosceles triangle with a base of 32-2X bisects the base vertically.

Therefore, half of an isosceles triangle can be transformed into a right triangle by Pythagorean theorem.

The square of 8 +( 16-X) = the square of x gives X= 10.

2. The same Pythagorean theorem

The topic is a bit unclear, that is, the distance from the bottom of the ladder to the bottom of the wall is 0.7M

It turns out that the distance from the stair head to the corner is A=(2.5 square -0.7 square), and the root sign is =2.4M

After sliding for 0.4, the distance from the stair head to the corner is B=2.4-0.4=2M.

At this time, the distance from the bottom of the ladder to the corner is (2.5 square -2 square). Root number =1.5m.

Then it slipped away1.5-0.7 = 0.8m.

3. A triangle with sides 3, 4 and 5 is a right triangle with 3 square +4 square =5 square.

So it becomes an area problem. CD=3*4/5=2.4。

Pythagoras theorem is not yet familiar.

Remember the side length ratio of several fixed right triangles.

Isosceles right angle 1: 1: root number 2

Right angle 30 1: root number 3: 2

There are also commonly used right-angled triangles, such as 3: 4: 5.

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