Because the base and height of a triangle are two related quantities, the base changes and the height also changes, and it is known that the base × height ÷2= the area of the triangle, so the area of the triangle is certain, and its base and height are inversely proportional.

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.

Extended data

Calculation formula of triangle area

1, given that the base of a triangle is a and the height is h, then S=ah/2.

2. It is known that two sides of a triangle are A and B, and the included angle between the two sides is C, so the area of the triangle is the product of two sides multiplied by the sine value of the included angle, that is, S=(absinC)/2.

3. Let three sides of a triangle be A, B and C, and the radius of inscribed circle be R, then the area of the triangle is S=(a+b+c)r/2.

4. Let the three sides of the triangle be A, B and C respectively, and the radius of the circumscribed circle be R, then the area of the triangle is A, B and c/4r. ? [2]?

5. In the right-angled triangle ABC (AB is perpendicular to BC), the area of the triangle is equal to half of the product of two right-angled sides, namely:

S=AB×BC/2

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