Place two rectangular pieces of paper as shown in the figure, so that a vertex of one of the rectangular pieces of paper just falls on one edge of the other rectangular piece of paper, then ∠ 1 + 2=______ Degree

As shown in the figure, connect the two intersection points. According to the parallelism of the two sides of the rectangle, we can get ∠ 1 + ∠ 2 + ∠ 3 + ∠ 4 = 180 ° and the angle of the rectangle is equal to 90 °, the angle of the rectangle is equal to 90 °, the angle of the rectangle is equal to 90 °, the angle of the rectangle is equal to 90 °, the angle of the rectangle is equal to 90 °, and the angle of the rectangle is equal to 90 °. So the answer is: 90

Find a piece of paper, draw a cube, connect three vertices to form an equilateral triangle, and ask what is the degree of an angle? (is it for expansion or solid?)

Stereoscopic
It's said that it's an equilateral triangle. How many degrees can it be
60 degrees
Teach you how to draw
Take any vertex
Just connect the three vertices adjacent to that vertex

As shown in the figure, there is a square paper with a gray triangle on it. Its vertices are located at the intersection of two grid lines. If the area of the gray triangle is 214 square centimeters, what is the area of the square paper? （　　）
A. 11B. 12C. 13D. 14

The side length of checkerboard paper is x, x2-12 · x · 12x-12 · 12x · 34x-12 · x · 14x = 214x2 = 12. So the area of checkerboard paper is 12, so choose B

As shown in the figure below, fold up a piece of paper. Given the angle 1 = 60 degrees, calculate the angle 2 = ()

180-(180-90-30)=120

It is known that the major axis of the ellipse is 12. The eccentricity e = 3 / 1, and the focus is on the x-axis. The standard equation of the ellipse is obtained

Your eccentricity is wrong. I think it should be 1 / 3. Let the elliptic equation be x2 / A2 + Y2 / B2 = 1 ∵ the major axis be 12 and the focus be on the X axis ∵ 2A = 12 → a = 6 ∵ e = 1 / 3 = C / a → C = 2 and C2 = A2-B2 ∵ B2 = 32 ∵ the elliptic equation be x2 / 36 + Y2 / 32 = 1 (the 2 after all letters are the power of 2)

Focus on the y-axis, C = 3, e = 3 / 5, find the standard equation of ellipse

Because C = 3, e = C / a = 3 / 5
So a = 5, B = 4
Because the focus is on the y-axis
So the equation is Y & # 178 / 25 + X & # 178 / 16 = 1

A = 4, B = 1, the focus writes the standard equation of the ellipse on the x-axis~

The focus is on the X axis
x^2/4^2+y^2/1^2=1
Namely: x ^ 2 / 16 + y ^ 2 = 1

Find the standard equation of ellipse which is suitable for the following conditions: 1. Focus on x-axis, a = B, e = 1 / 3; 2. Focus on y-axis, C = 3, e = 5 / 3

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The focus of the standard equation for finding ellipse is on X axis and passes through points (2,0) and (0,1)
The standard equation of ellipse suitable for the following two conditions
1. The focus is on the x-axis and passes through points (2,0) and (0,1)
2. After a (2, - radical 2 / 2), B (- radical 2, - radical 3 / 2)

(1) If the focus is on the x-axis and passes through points (2, 0) and (0, 1), then a = 2, B = 1
The elliptic equation is x ^ 2 / 4 + y ^ 2 = 1
(2) If the focus is on the X axis, let the equation be x ^ 2 / A ^ 2 + y ^ 2 / b ^ 2 = 1 a > b > 0
The coordinates of a (2, - radical 2 / 2) and B (- radical 2, - radical 3 / 2) are substituted respectively
4/a^2+1/2b^2=1 ①
2/a^2+3/4b^2=1 ②
② The elliptic equation of a ^ 2 = 8, B ^ 2 = 1 is x ^ 2 / 8 + y ^ 2 = 1
If the focus is on the Y axis, let the equation be y ^ 2 / A ^ 2 + x ^ 2 / b ^ 2 = 1 a > b > 0
It can be solved that a ^ 2 = 1, B ^ 2 = 8, which is contradictory to a > b > 0
To sum up, we know that the elliptic equation is x ^ 2 / 8 + y ^ 2 = 1

To find the standard equation of an ellipse satisfying the following conditions, one focus of the ellipse is (- 4,0), and the focus of the ellipse and X axis is (5,0)
What information can we get from the sentence that the focus of x-axis is (5,0)?

Is it the point of intersection with the x-axis?
If it is the intersection with the x-axis, and because the focus is on the x-axis, the long half axis is a / 2 = 5
And C = 4
b^2=a^2-c^2=84
The equation is x ^ 2 / 100-y ^ 2 / 84 = 1

Place two rectangular pieces of paper as shown in the figure, so that a vertex of one of the rectangular pieces of paper just falls on one edge of the other rectangular piece of paper, then ∠ 1 + 2=______ Degree