Triangle area refers to the plane area of a triangle obtained through measurement and calculation, which is applied to primary school mathematics.

There are several formulas for calculating the area of a triangle:

1, given the triangle base a and height h, then S=ah/2. Given three sides a, b and c of a triangle, then

(Helen formula) (p=(a+b+c)/2)

S=sqrt[p(p-a)(p-b)(p-c)]

= sqrt[( 1/ 16)(a+b+c)(a+b-c)(a+c-b)(b+ c-a)]

= 1/4 sqrt[(a+b+c)(a+b-c)(a+c-b)(b+c-a)]

2. Given two sides A and B of a triangle, the included angle between the two sides is C, then S= 1/2absinC, that is, the product of the two sides is multiplied by the sine value of the included angle.

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

5. Let the three sides of a triangle be A, B and C respectively, and the radius of the circumscribed circle be R, then the triangle area =abc/4R.

Attributes of triangle:

1. On the plane, the sum of the interior angles of a triangle is equal to 180 (interior angle sum theorem). On the plane, the sum of the exterior angles of a triangle is equal to 360 (exterior angle sum theorem). On the plane, the outer angle of a triangle is equal to the sum of two non-adjacent inner angles. There are at least two acute angles among the three internal angles of a triangle.

2. 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. The sum of any two sides of a triangle is greater than the third side, and the difference between any two sides is less than the third side. In a right triangle, if an angle is equal to 30 degrees, then the right side opposite to the 30-degree angle is half of the hypotenuse.

3. The sum of squares of two right-angled sides of a right triangle is equal to the square of the hypotenuse (Pythagorean theorem). The center line of the hypotenuse of a right triangle is equal to half of the hypotenuse.