Circumference formula and area formula of semicircle fast

Circumference formula and area formula of semicircle fast

Circumference of semicircle = 3.14 × diameter △ 2 + diameter
Semicircle area = 3.14 × radius & # 178; △ 2

Each album has 36 pages, each page can put 2 photos, 6 such albums put a total of how many photos?

2 × 36 × 6 = 72 × 6 = 432 (sheet)
A: there are 432 photos in 6 albums

Fill 9-17 in the space to make the sum of horizontal, vertical and diagonal equal

12 17 10
11 13 15
16 9 14

Exercise 1.2
T1: it is known that in △ ABC, D is the midpoint of BC, de ⊥ AB, DF ⊥ AC, e and f respectively, and de = DF
Prove that △ ABC is an isosceles triangle

It is proved that a right triangle BDE is congruent with a right triangle CDF, so angle B is equal to angle c, so AB = AC, so isosceles

Optimizing the test paper
The answer to "Jiangsu edition · optimization test paper · Mathematics Grade 9 Volume 2"!
I don't know the specific name, but there is such a line on the brow of this paper in my hand. The title of this paper is "Jiangsu version of Mathematics Grade 9 Volume 2 mid term test B"
Afternoon class, depending on the situation can add!

Classmate We all have a hard life Our teacher also classified 168 sets of answers If you get the answer Just leave me a message Please

A simple method to solve a problem with nine mathematical knowledge
The radius of an arc is 20m, and the chord of the arc is 32m. Calculate the length of the arc (accurate to 0.01M)!

2 π R × 32 / 40 square-16 square
2 π r = perimeter
32 / 40 square-16 square = center angle of arch arc length
Dividing by circumference is equal to arc length

As shown in the figure, the area ratio of fan-shaped OAB to ⊙ P is 90 ° and ⊙ P is tangent to OA and ob at points F and e respectively, and is tangent to arc AB at point C______ ．

Let PE be 1 and op = 2, then OC = 2 + 1. The area of sector OAB = 90 × π (2 + 1) 2360; the area of ⊙ P = π; the area ratio of sector OAB to ⊙ P is 3 + 224

The position relationship between the third circle and the circle
Given that the distance between the centers of the two circles is d = 5, and the radii of the two circles are two of the equation x-5x + 3 = 0, then the position relationship between the two circles is?
A. Intersection B. separation
C. Exo D. Intro

C
X1+X2=5,X1X2=3
That is, the sum of radius is equal to the center distance of two circles

In the past three years, the students of class two participated in the long-distance running team and the chorus team, and each of them participated in at least one activity. Among them, the number of people who participated in the long-distance running team accounted for 3 / 5 of the total number of the class, the number of people who participated in the chorus team accounted for 4 / 5 of the total number of the class, and the number of people who participated in both groups accounted for a fraction of the total number of the class

The answer is two in five
We can use the number of people who participate in the long-distance running team, plus the number of people who participate in the chorus, and then subtract the total number to get the number of people who participate in both teams
（3/5）+（4/5）-1=2/5

There are two barrels of oil. The big barrel of oil is 56 kg more than the small barrel of oil. If the small barrel of oil is used up to 4 kg, the big barrel of oil is four times as much as the small barrel of oil. How many kg do the two barrels of oil weigh?

56 + 4 = 60,60 ÷ (4-1) = 20,20 × 4 = 80 (big barrel), 20 + 4 = 24 (small barrel)