/sci/ - Science & Math

Is this legit?

>>3221366
Dark matter is at the moment just unexplained gravity. It seems to form the background of conglomerations of matter, or so it seemed as shown in that episode of Through the Wormhole.

Right then.

I thought it might be important because I watched a documentary voiced by Morgan Freeman (apparently he knows a lot about black holes). It said that entropy had been shown to increase by the square and not the cube (of radius I suppose) as might be expected for a volume, and this led to discovery of the holographic principle. You see the apparent relation.

/sci/ I got a doubt, I got 3 vectors
a) 20, 30°
b) 25, 125°
c) 30, 250°
so I know that I get around 7.6 from all of them, and I know the angle is -17.45° but I my formula °=tan(fx/fy) says otherwise.. can /sci/ help?
pic unrelated

Hi. physicsfag with not-so-great math skills, here.

I have a mass density function, call it p(r), and I don't know how to integrate to figure out the acceleration due to gravity on some object at position x. I know that the acceleration is proportional to the inverse of the square of the distance to the source.

I want to integrate G*p(r)/(x-r)^2 from r = 0 to r = x, then subtract from that the same integral from r = x to r = infinity to find the acceleration of x.. but I don't feel confident about this.