A closed figure composed of three line segments that are not on the same straight line is called a triangle. A figure enclosed by three straight lines on a plane or three arcs on a sphere. The figure surrounded by three straight lines is called a plane triangle; A figure surrounded by three arcs is called a spherical triangle, also known as a triangle.

Area formula: (1)S=ah/2.

(2) If the three sides A, B and C of a triangle are known, then (Helen formula) (p = (a+b+c)/2) s = √ [p (p-a) (p-b) (p-c)].

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

(3) Given the included angle C between two sides of triangle A and B, then S= 1/2 * absinC (4). Let the three sides of a triangle be A, B and C respectively, and the radius of the inscribed circle be R = (A+B+C) R/2.

(5) Let the three sides of the triangle be A, B and C respectively, and the radius of the circumscribed circle be R S=abc/4R.

(6). Find the area according to the trigonometric function:

S = absinc/2a/sina = b/sinb = c/sinc = 2r Note: where r is the radius of the circumscribed circle.

Area formula:

( 1)S=ah/2

(2) Given three sides A, B and C of a triangle, then (Helen formula) (p=(a+b+c)/2)

S=√[p(p-a)(p-b)(p-c)]

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

(3) Given the included angle C between a and b on both sides of a triangle, S = 1/2 * ABS Inc.

(4) Let the three sides of the triangle be A, B and C respectively, and the radius of the inscribed circle be R..

S=(a+b+c)r/2

(5) Let the three sides of the triangle be A, B and C respectively, and the radius of the circumscribed circle be R..

S=abc/4R

(6). Find the area according to the trigonometric function:

s = absinC/2 a/sinA = b/sinB = c/sinC = 2R

Note: where r is the radius of the circumscribed circle.