a
We know the angle, the adjacent side and we are looking for the opposite side = O
The tangent relates these = opp/ adj
tan (37°) = O / 6.5
Solve this → 6.5 * tan (37°) = O
b
We know the angle, the adjacent side and we are looking for the hypotenuse, H
The cosine relates these = adj / hyp
cos (37°) = 6.5 / H rearrange ahd solve this
H = 6.5 / cos (37°)
Add H + O to get the tree height
Let me know if you get stuck