*The angle between the line from the earth to the sun and the line from the mars to the sun RIGHT NOW. I only found the right ascention and declination of Mars, which is measured with respect to Earth. However, I am a bit confused about the March equinox, so I am not sure how I can deduce the angle I am looking from from the information I have.
According to Mathematica, using Entity["Planet","Earth"]["HelioCoordinates"] and Entity["Planet","Mars"]["HelioCoordinates"], the current Earth-Sun-Mars angle is 4.35 degrees. But this does not assume that they are in coplanar orbits; it uses their actual non-coplanar orbits.
If you want to impose coplanarity, you have to explain in more detail how you want to mathematically do that. For example, if you project the heliocentric coordinates onto the ecliptic plane by using only the $x$ and $y$ coordinates, then the angle is 4.30 degrees.