1)ab= 15 ac=20 According to the right triangle law, BC = √ (15 *15+20 * 20) = 25.

2) According to the right triangle area formula, two right angles are multiplied by 2 = area = bottom multiplied by height divided by 2.

Get ab * AC/2 = BC * ad/2ad =15 * 20/25 =12.

2

Make a straight line perpendicular to B and C through the armor, and through B and C in D, we can know that A and D are an isosceles right triangle, and A and B form 80. According to the law of right isosceles triangle, we can know that b and d are 40 √ 2.

At this time, butyl = 100-40 √ 2 was found.

According to the right triangle law, A-C = √ (A-D Square +A-D Square) = about 7 1KM.

three

The area of a small square is 1, and the unit distance (the distance between points) is 1.

According to the distance formula between two points in the coordinate system, AB = √10bc = √ 5ac = √17.

Then that sum of line segment with a circumference of 3 is equal to =9.5.

Since the square of AB+the square of BC = the square of AC satisfies Pythagoras' law.

So ABC is a right triangle.

The area is the product of two right angles and then divided by 2.

Area =(√5*√ 10)/2=5√2/2=3.5