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The circumference of a rectangle is 20 cm. If the length is 9 cm, the width is 1 cm. If the length is 8 cm, the width is 2 cm With the same perimeter Judge whether it is an inverse proportion and state the reasons
It's not inverse proportion, because 2A + 2B = C is the product of two numbers in addition. When one is added, these two quantities are inverse proportion!
If the perimeter of a rectangular photo frame is 40 cm and the side length is 8 cm, the maximum area that can hold photos is 10 cm
Is it 40 * 8?
Calculate the other side first. 40 / 2-8 = 12 cm
Recalculated area 12 * 8 = 96 (square centimeter)
Given the three sides of a triangle, what is the formula for calculating its area?
Is: only know the side length, do not know the angle, how to find the area of the triangle?
Yes. As for Helen's formula:
S = sqrt(s*(s-a(1))*(s-a(2))*(s-a(3)))
S is the half circumference
What is the general formula of triangle area?
What's the general formula for the area of a triangle,
It seems that under the root sign, the difference between the two sides is divided by two
Well, for the convenience of answer, let three sides be a, B and C respectively
S = radical (P (P-A) (P-B) (P-C))
p=1/2(a+b+c)
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