The area of a semicircle is 56.52 square decimeters. What's its circumference

The area of a semicircle is 56.52 square decimeters. What's its circumference

1.56.52x2 = 113.04 square decimeter 2. Circle s = π r square 3.113.04/3.14 = 36dm4.36/2 = 18dm

It is easy to calculate 3 × (2 / 9 + 2 / 15) - 0.4
Recursive calculation, can be simple and easy!
3 × (2 / 9 + 2 / 15) - 0.4
75 × 5 / 7 + 2 / 7 △ 4 / 3
1 / 6 + 4 - (1 / 8 + 1 / 6)
15 / 28 △ 0.3 × 7 / 50
32 / 45 (2 / 3 + 2 / 5)
(7-0.25) △ 9 / 16

3 × (2 / 9 + 2 / 15) - 0.4
=3×2/9＋3×2/15—0.4
=2/3＋2/5—2/5
=2/3
75 × 5 / 7 + 2 / 7 △ 4 / 3
=3 / 4 × 5 / 7 + 2 / 7 × 3 / 4
=3/4×（5/7＋2/7）
=3/4×1=3/4
1 / 6 + 4 - (1 / 8 + 1 / 6)
=1/6＋4—1/8—1/6
=(1/6—1/6)＋(4—1/8)
=3 and 7 / 8
15 / 28 △ 0.3 × 7 / 50
=15/28×10/3×7/50
=1/4
32 / 45 (2 / 3 + 2 / 5)
=32/45×15/16
=512/675
(7-0.25) △ 9 / 16
=27/4×16/9
=12

In the triangle ABC, AB equals 3aD, be equals EF equals FC, CA equals 3cg. If connecting dgfe into a quadrilateral, the quadrilateral takes up the area of triangle ABC
Please write down the process, my points are limited, I thank you first!

4/9
It's easy to draw a graph. Let the area of triangle ABC be 1, then the area of triangle CGF is 1 / 9, the area of triangle ADG and triangle BDE are 9 / 2, so the area of quadrilateral is 1-1 / 9-2 / 9-2 / 9 = 4 / 9

In all the permutations A1, A2, A3, A4, A5, A6 of 1, 2, 3, 4, 5, 6, the number of different permutations satisfying the conditions A1 > A2, A3 > A4, A5 > A6 is

In order to form an permutation suitable for the condition, we need three steps to complete 1. Because six numbers are different from each other, we can get an inequality suitable for the condition by taking any two of the six numbers, which can form C (6,2) suitable 2. For each result obtained in the first step, we can use the same method from the remaining four numbers

Draw the trapezoidal diagonal, so as to form four triangles. Mark the upper bottom as a and the area of the lower bottom as B. question: how to prove the area of the triangle on the upper bottom

Because the top and bottom of the trapezoid are parallel, it is easy to prove that S1 and S4 are similar, and the ratio of area is S1: S4 = A2: B2 (1) (S1 + S3): (S4 + S3) = A: B S3: S4 = A: B (2) S1: S3 = A: B (3) similarly, S1: S2 = A: B (4) S2 = S3 from (3) and (4). Your question may be a little inaccurate, you can get the result according to the above method

If f (2x + 1) = lgx, then f (21)=______ ．

According to the meaning of the question, let 2x + 1 = t (t ＞ 1), then x = 2T − 1, that is, f (x) = lg2x − 1 (x ＞ 1); {f (21) = lg221 − 1 = - 1

Xiaohua's room is 4.5 meters long and 2 / 3 and 8 meters wide. It needs white paint to paint the walls and roof. The area of doors and windows is 6 square meters, and the average paint is 0.4 kg per square meter. How many kg of paint do you need?

Painting area
4.5x(4.5x2/3)+4.5x2.8x2+(4.5x2/3)x2.8x2-6
=13.5+42-6
=49.5 square meters
Need paint
0.4x49.5 = 19.8kg

M. N is the two golden section points of line ab. AB = 1, find Mn

M. N is the two golden section points of line ab
therefore
AN=（√5-1）/2
MB=（√5-1）/2,
AM=AB-MB
MN=AN-AM
=AN-（AB-MB）
=AN+MB-AB
=（√5-1）-1
==√5-2

Two triangles of equal area can form a parallelogram______ (judge right or wrong)

Two triangles of equal area may not form a parallelogram

Am or PM in the morning? I always mess up

Am (ante meridiem) in the morning
PM (post meridiem) in the afternoon