Question 1037406
Doorway to Camera, 16 meter leg
Parking Lot Edge to Camera, 24 meter hypotenuse
Parking Lot Edge to Doorway, 28 meter leg



This is not a right triangle.  Change the names of the sides to this:

Doorway to Camera, 16 meter side
Parking Lot Edge to Camera, 24 meter side
Parking Lot Edge to Doorway, 28 meter side
...
and to be sure,
{{{16^2+24^2<>28^2}}}
{{{256+576<>784}}}
{{{832<>784}}}


Law Of Cosines will use the unknown angle at the camera.  The distance from doorway to edge of the parking lot is the side opposite the camera.
-
{{{16^2+24^2-2*16*24*cos(c)=28^2}}}


{{{832-2*16*24*cos(c)=28^2}}}
{{{-2*16*24*cos(c)=28^2-832}}}
{{{cos(c)=(28^2-832)/(-2*16*24)}}}
{{{cos(c)=48/(2*16*24)}}}
{{{cos(c)=1/(16)}}}


Angle measure c is arcos(1/16)  or  {{{cos^-1(1/16)}}}.
86 degrees.