Calculate angle of triangle Python

Question

I'm trying to find out the angle of the triangle in the following, I know it should be 90 degrees, however I don't know how to actually calculate it in the following:

Here's what I've tried:

angle = math.cos(7/9.899)
angleToDegrees = math.degrees(angle)

returns: 43.XX

What am I doing wrong?

Solution 1

It's a little more compicated than that. You need to use the law of cosines

>>> A = 7
>>> B = 7
>>> C = 9.899
>>> from math import acos, degrees
>>> degrees(acos((A * A + B * B - C * C)/(2.0 * A * B)))
89.99594878743945

This is accurate to 4 significant figures. If you provide a more precise value of C, you get a more accurate result.

>>> C=9.899494936611665
>>> degrees(acos((A * A + B * B - C * C)/(2.0 * A * B)))
90.0

Solution 2

You can use this also.

print(str(int(round(math.degrees(math.atan2(x,y)))))+'°')

This accepts two inputs as two heights of the triangle and you can get the output angle in proper degree format.

Comments

[Shannon Hochkins]

This just gave me an even 45.00

[Shannon Hochkins]

is that not what math.degrees does? converting radians to degrees/angles

[Shannon Hochkins]

That worked great, you wouldn't mind explaining it a bit more though would you?

[John La Rooy]

@ShannonHochkins, follow the link to wikipedia for the explanation. It's really off-topic for this site.

[Shannon Hochkins]

Why is it off topic? I asked how to calculate this, usually an answer is best when it has better descriptions rather than just the code.

[John La Rooy]

@ShannonHochkins, because it's math. You could try asking for an explanation on math.stackexchange.com

[Teepeemm]

Trig functions are for when you have an angle of 90 degrees, and you're interested in some other angle.

[Teepeemm]

It does convert radians to degrees. But tan(1) is not radians to begin with. The fact that you are treating it as radians is wrong.

[TehTris]

@Teepeemm trig funcs are for all triangles, they are just simpler when a 90deg angle is involved.

[Teepeemm]

This code assumes that OP's marked angle is 90degrees, and then gives the acute angle next to input "BC".