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What are the formulas for calculating the area in the first volume of the fifth grade mathematics of Beijing Normal University?
=( 1/2)* bottom * height

S=( 1/2)*a*b*sinC (C is the included angle between a and b)

Bottom * Height /2

The height x of the base is divided by 2/2 (the sine of the included angle of the length x of both sides).

Circumference of s = 1/2 * radius of inscribed circle

S=( 1/2)* bottom * height

s=( 1/2)*a*b*sinC

The sum of the two sides is greater than the third side, and the difference between the two sides is less than the third side.

Large angle versus large edge

Circumference c= sum of three sides a+b+c B+C.

zone

S= 1/2ah (bottom * height /2)

S= 1/2absinC (half of sine product of two sides and included angle)

s= 1/2acsinB

s= 1/2bcsinA

Under s= radical sign: p(p-a)(p-b)(p-c) where p= 1/2(a+b+c).

This formula is called Helen formula.

Sine theorem:

Sina /a=sinB/b=sinc/C

Cosine theorem:

A 2 = b 2+c 2-2bc Xhosa

B 2 = A 2+C 2-2AC Cosbu

C 2 = A 2+B 2-2AB Xhosa

Two sides of a triangle are larger than the third side.

Triangle area = base * height /2

The sum of the internal angles of the triangle = 180 degrees.

Find the area (upper bottom+lower bottom) × height ÷2

Triangle area = base * height /2

Triangle area formula:

Bottom * Height /2

The sum of the internal angles of a triangle is 180 degrees.