Math.Atan2 Method

毕业刚到两年，结果连三角函数的性质、 定义域、值域，图像等忘得一干二净。可能是在毕业前就已经忘掉了。
今天画个图需要算几个点的坐标。想起了，他但是很多东西都忘了。
折腾了半天才明白了一点儿，呵呵，
我这次用到了 Math.Tan， Math.Atan2 函数，下面把这两个函数在msdn上的解释拷贝到下面供以后方便查找。

Math.Tan Method 

Returns the tangent of the specified angle.

Parameters

a

An angle, measured in radians.

Return Value

The tangent of a. If a is equal to NaN, NegativeInfinity, or PositiveInfinity, this method returns NaN.

The angle, a, must be in radians. Multiply by π/180 to convert degrees to radians.

Math.Atan2 Method 

Returns the angle whose tangent is the quotient of two specified numbers.

Parameters

y 

       The y coordinate of a point.

x

           The x coordinate of a point.

Return Value

An angle, θ, measured in radians, such that - π ≤ θ ≤ π, and tan( θ) = y / x, where ( x, y) is a point in the Cartesian plane. Observe the following:

• For (x, y) in quadrant 1, 0 < θ < π/2.

• For (x, y) in quadrant 2, π/2 < θ≤π.

• For (x, y) in quadrant 3, -π < θ < -π/2.

• For (x, y) in quadrant 4, -π/2 < θ < 0.

The return value is the angle in the Cartesian plane formed by the x-axis, and a vector starting from the origin, (0,0), and terminating at the point, (x,y).