The problem of the angle of the line segment ~! ~! ~!

23246206

There are two line segments AB, AC intersect with a point A (x, y)
The segment AB coordinates are A (x, y) B (x1, y1)
Line segment AC coordinates are A (x, y) C (x2, y2)

How to calculate or judge whether the included angle A is less than 90 degrees
How to write the functions of Zheng Xuan, Yu Xuan, Tangent, Cotangent called in C #?
I am new to C # mathematical functions
Please advise

lygzgs

lz check the knowledge of the vector, you can find directly
It ’s better to do it yourself

23246206

Can you briefly introduce it?

23246206

Please enlighten me ~!

allenrun

Math.function name
such as
Math.sin () or something.

Then the algorithm is not difficult to analyze geometric principles.

wenmy715

Math.Sin (double x)
Math.Cos (double x)
.....
All static methods are called directly