A 8:27 B 2:3 C 4:9 D 2:9
2. No matter what the value of m is, the straight line y+ 1=m(x-2) always passes through a fixed point whose coordinate is (d).
A.( 1，-2) B.(- 1，2) C.(-2，- 1) D.(2，- 1)
3. It is known that m and n are two non-coincident straight lines, and α, β and γ are three non-coincident planes. The following four propositions are correct (A).
A. if m⊥α and m⊥β, α ∧β.
B If α ⊥ γ, β ⊥ γ, α ∧β
C. if m? α，n？ β, m∨n, and then α ∨ β.
D. if m and n are straight lines in different planes, m? α，m∧β，n？ Beta, then alpha sigma beta.
4. Given a tetrahedron whose four sides are equilateral triangles, the side length is 2 and the surface area is (4√3).
5. Find the three points of the known triangle A (4 4,0) B (8,10) C (0,6).
Linear equation of (1)AC side height
The equation of straight line AC is y=- 1.5x+6.
The linear equation of AC side height is y- 10=2(x-8)/3, that is 2x-3y+ 14=0.
(2) The equation of the straight line passing through point A and parallel to BC is y-0=0.5(x-4), that is, y=0.5x-2.
(3) Find the height of BC side
The equation of BC line is y=0.5x+6.
The equation of the line with BC side height is y=-2(x-4), that is, y=-2x+8.
The height and length of BC side H= 16√5/5.
6. The oblique perspective view of a horizontal plane figure is an isosceles trapezoid with a base angle of 45 and waist and upper and lower sides of 1, so the volume of this plane figure is (2+√2).
7. The inclination range of the straight line Xcosθ+y+m=0 is {α|0≤α≤π/4 or 3 π/4≤α < π}.
8. The inclination of the straight line L is [π/4,2π/3], and the range of the slope of the straight line L is {k|k≥ 1 or k≤-√3}.
9. The molecular structure of methane is that a central carbon atom and four peripheral hydrogen atoms form a tetrahedron, and the central carbon atom and four hydrogen atoms are equidistant and connected into four line segments, and the angle formed by them is θ, so the value of cosθ is (a).
A. Negative one third B. One third C. Half D. Negative one half
10. if the straight line L 1: AX+2Y+6 = 0, the straight line L2: X+(A- 1) Y+(A? -1)=0 Parallel and non-coincident, then the value of a is (-1).