What is the value of the number 2 if it is in the ten-thousands place?
1 answer:
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This question has this set of answer choices:
a) when the plane cuts three faces of the cube, separating one corner from the others
b) when the plane passes through a pair of vertices that do not share a common face
c) when the plane is perpendicular to the base and intersects two adjacent vertical faces
d) when the plane makes an acute angle to the base and intersects three vertical faces
e) not enough information to answer the question
The right answer is the first choice: a) when the plane cuts three faces of the cube, separating one corner from the others
You can see a picture of this case in the figure attached: as you can see the cross section (in pink) is a triangle.
a) when the plane cuts three faces of the cube, separating one corner from the others
b) when the plane passes through a pair of vertices that do not share a common face
c) when the plane is perpendicular to the base and intersects two adjacent vertical faces
d) when the plane makes an acute angle to the base and intersects three vertical faces
e) not enough information to answer the question
The right answer is the first choice: a) when the plane cuts three faces of the cube, separating one corner from the others
You can see a picture of this case in the figure attached: as you can see the cross section (in pink) is a triangle.
Rewrite the boundary lines <em>y</em> = -1 - <em>x</em> and <em>y</em> = <em>x</em> - 1 as functions of <em>y </em>:
<em>y</em> = -1 - <em>x</em> ==> <em>x</em> = -1 - <em>y</em>
<em>y</em> = <em>x</em> - 1 ==> <em>x</em> = 1 + <em>y</em>
So if we let <em>x</em> range between these two lines, we need to let <em>y</em> vary between the point where these lines intersect, and the line <em>y</em> = 1.
This means the area is given by the integral,
The integral with respect to <em>x</em> is trivial:
For the remaining integral, integrate term-by-term to get
Alternatively, the triangle can be said to have a base of length 4 (the distance from (-2, 1) to (2, 1)) and a height of length 2 (the distance from the line <em>y</em> = 1 and (0, -1)), so its area is 1/2*4*2 = 4.
