The height of the triangle is higher than the area × 2 base.

S= 1/2 bottom× height: a stands for bottom, h stands for height: h = 2s/a.

Ordinary triangles are divided into ordinary triangles (three sides are unequal) and isosceles triangles (isosceles triangles with unequal waist and bottom and isosceles triangles with equal waist and bottom, that is, equilateral triangles); According to the angle, there are right triangle, acute triangle and obtuse triangle, among which acute triangle and obtuse triangle are collectively called oblique triangle.

Method 1:

1, acute triangle: all three internal angles of the triangle are less than 90 degrees.

2. Right triangle: One of the three internal angles of the triangle is equal to 90 degrees, which can be recorded as Rt△.

3. obtuse triangle: one of the three internal angles of the triangle is greater than 90 degrees.

Decision method 2:

1, acute triangle: the largest of the three internal angles of a triangle is less than 90 degrees.

2. Right triangle: The largest of the three internal angles of a triangle is equal to 90 degrees.

3. obtuse triangle: the largest of the three internal angles of a triangle is greater than 90 degrees and less than 180 degrees.

Among them, acute triangle and obtuse triangle are collectively called oblique triangle.

Extended data:

Area formula

1, (area = bottom × height ÷2). Where A is the base of the triangle and H is the height corresponding to the base) Note: All three sides can be the base, which should be understood as: half of the product of the heights corresponding to the three sides is the area of the triangle. This is the basis of finding the length of line segment by area method.

2、

(Among them, the three angles are ∠A, ∠B and ∠C respectively, and the opposite sides are ∠ A, ∠ B and ∠ C respectively. See trigonometric function)

3.(L is the center line of the height side)

4, (Helen formula), of which?

Nature:

1. On the plane, the sum of the interior angles of a triangle is equal to 180 (interior angle sum theorem).

2. On the plane, the sum of the outer angles of a triangle is equal to 360 (the theorem of the sum of outer angles).

3. On the plane, the outer angle of a triangle is equal to the sum of two non-adjacent inner angles.

Inference: An outer angle of a triangle is greater than any inner angle that is not adjacent to it.

4. There are at least two acute angles among the three internal angles of a triangle.

5. At least one angle in the triangle is greater than or equal to 60 degrees, and at least one angle is less than or equal to 60 degrees.

References:

Baidu encyclopedia-triangle