What is the value of θ for the acute angle in a right triangle?

sin (θ) = cos (73°)

Now we can see that

θ + 58º = 90º

θ = 90º - 58º

θ = 32º

I don't really know what you mean by "for the acute angle in a right triangle," since both of the other angles in a right triangle are acute. But there are 2 angles that have the same sin as sin (32º).

Those two angles are:

32º (acute) ... and ... 180º - 32º = 148º (obtuse)