A semicircle with a diameter of 8dm and a circumference of______ DM, the area is______ dm2．

A semicircle with a diameter of 8dm and a circumference of______ DM, the area is______ dm2．

Semicircle perimeter: 3.14 × 8 △ 2 + 8, = 12.56 + 8, = 20.56 (decimeter); semicircle area: 3.14 × 8 △ 2, = 3.14 × 8, = 25.12 (square decimeter); answer: semicircle perimeter is 20.56 decimeter, area is 25.12 square decimeter

The area of an isosceles right triangle is 8dm2. The area of an isosceles right triangle is 8dm2______ The circumference is______ ．

The square is as follows: the area is 8 × 8 = 64 (square decimeter); if the area of a large square is 64 square decimeter, its side length is 8 decimeter; if the perimeter is 8 × 4 = 32 (decimeter); a: its area is 64 square decimeter, its perimeter is 32 decimeter. So the answer is 64 square decimeter, 32 decimeter

The perimeter of a hospital is 31.4dm, its diameter is () DM, its radius is () DM, and its area is () DM square

1 question:
　　d=C÷π
　　=31.4÷3.14
　　=10（dm）
2 question:
　　r=d÷2
　　=10÷2
　　=5（dm）
3 questions:
　　S=πrr
　　=3.14x5x5
= 78.5 (square decimeter)

It is known that in △ ABC, ∠ a = 60 ° and the bisectors of ∠ ABC and ∠ ACB intersect at point O, then the degree of ∠ BOC is 0______ Degree

∵∠A=60°∴∠ABC+∠ACB=120°∴∠BOC=180°-12（∠ABC+∠ACB）=120°．

Write a system of linear equations of two variables, so that the coefficients of the unknowns are integers, and the solution is {x = 1,2,y = 2,3}
It's a process, quick

2x＋3y＝3
4x＋3y＝4
If you know all the solutions, you can just round up the whole number
allied
6y－2x＝3
9y＋4x＝8
Any combination of the two is OK

It is known that vector a = (- 2,5) the modulus of vector B is equal to twice the modulus of vector A. if vector B is opposite to vector a, then vector B and so on

Just accidentally wrong, it should be known from the meaning of the question that B = - 2A = (4, - 10) is actually the direct use of vector coordinate operation, the reverse is collinear, so B = ma (M is a real number and M is less than 0) and the module length is twice, so m = - 2
Note: because I can't change the font, I didn't show the vectors a and B. the handwritten ones need to be marked with arrows

In the triangle ABC, ab = AC, ∠ a = 120 °, the intersection of AB and BC in M.N. what is the quantitative relationship between BN and NC? Explain the reason

Link an
The perpendicular of ∵ ab
Ψ am = BM angle amn = ∠ BMN = 90 ° Mn = Mn (common side)
∴△BMN≌△AMN （SAS）
Also, ACB = 30 degree
∴AN=½CN
∵AN=BN
∴NC=2BN

Decomposition factor: X3 + 5x2y-24xy2

The original formula is x (x2 + 5xy-24y2) = x (x + 8y) (x-3y)

It is known that the left and right focal points of the ellipse x2 / 16 + Y2 / 12 = 1 are located in F1, F2, M is the point on the ellipse, and N is the midpoint of MF1. If | on | = 1, then the length of | MF1 |?

Let m coordinate be (x1, Y1) because F1 (- 2,0) and n be the midpoint of MF1. So n coordinate is ((x1-2) / 2, Y1 / 2) because | on | = 1, then [(x1-2) / 2] ^ 2 + (Y1 / 2) ^ 2 = 1, and because m is a point on the ellipse, then X1 ^ 2 / 16 + Y1 ^ 2 / 12 = 1. From the above two equations, we get m (4,0), so the length of | MF1 | is 4 -

The two right sides of a right triangle are 6cm and 8cm respectively. The 6cm long right side is a circle of the axis of rotation, and the conic volume is obtained
Less cubic centimeter

Cone bottom radius = 8 cm. Height = 6 cm
Volume = 8 × 8 × 3.14 × 6 × 1 / 3 = 401.92 cm3