Ограничения: время – 1s/2s, память – 64MiB Ввод: input.txt или стандартный ввод Вывод: output.txt или стандартный вывод
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A projectile is launched in three-dimensional space and travels through the air, forced down-
ward by gravity, but otherwise unaffected by friction or other forces. There is a vertical target plane
through which the projectile will eventually penetrate, unless it travels away from or parallel to the
target plane. In this problem, we are given the initial velocity `vec{v}` (i.e. the speed and direction as a
3-dimensional vector) of a projectile and the position of a target plane and are asked to compute
the exact point in 3-dimensional space at which the projectile impacts the target plane.
The projectile is launched at time `t\ =\ 0` from the origin `(0,\ 0,\ 0)` traveling at a velocity
`vec{v}\ =\ (v_x,\ v_y,\ v_z)` whose speed components in the `x`-, `y`- and `z`-direction are `v_x`, `v_y` and `v_z` m/sec, respectively. The force of gravity causes a downward (i.e. negative `z`-direction) acceleration on the
projectile of `9.8\ m//sec^2`. I'm sure you recall from your physics class that the position of the projectile after `t` seconds is
`(v_x\ t,\ v_y\ t,\ v_z\ t\ -\ {9.8t^2}/2)`
The target plane is a vertical plane consisting of all points `(x,\ y,\ z)` satisfying a linear equation
`"ax"\ +\ "by"\ =\ c`.
Input Format
The input contains one or more trials, each described on two lines of input followed by an
empty line of input. The first line of each trial contains three integers `v_x,\ v_y,\ v_z` defining the initial
velocity `vec{v}\ =\ (v_x,\ v_y,\ v_z)` of the projectile. The second line of each trial contains three integers
`a,\ b,\ c` defining the vertical target plane `"ax"\ +\ "by"\ =\ c`.
Output Format
For each trial, compute the time `t` (in seconds after the launch) and the point `(x,\ y,\ z)` at which
the projectile impacts the target plane. Report `t`, `x`, `y` and `z` rounded to two decimal places as shown
in the output sample. If the projectile travels away from or parallel to the target plane, report that
instead.
Sample Input
1 1 0
1 1 10
1 1 10
-1 1 -1
-1 -1 10
1 1 10
34 -25 201
-10 5 -32
Sample Output
Impacts after 5.00 seconds at position (5.00, 5.00, -122.50)
Travels parallel to plane
Travels away from plane
Impacts after 0.07 seconds at position (2.34, -1.72, 13.81)
Source: California State Polytechnic University Programming Contest, Spring 2008