so now, our right-triangle has an acute angle called u, with the opposite side, length 2, the hypotenuse, length 3, and the other side, length sqrt(5) (by pythagoras' theorem).
so cos(u) = adj/hyp = sqrt(5)/3 ...but wait, we are in the second quadrant, cosine is negative. so cosu = - sqrt(5)/3
the tangent is also negative in the second quad. so
tanu = - opp/adj = - 2/sqrt(5)
and we have:
u = arcsin(2/3) = 41.8103149 degrees = 0.729727656 radians
This is my 14 th post!!!!