Consider the schematic diagram given below,
In the diagram, AB represents the height of the tree, and point C is the location of the observer.
The angle of of elevation to the top of the tree is the angle BCA here.
This angle can be calculated as,
![\begin{gathered} \tan (\angle BCA)=(AB)/(BC) \\ \tan (\angle BCA)=(45)/(20) \\ \tan (\angle BCA)=2.25 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/6laxhakd7y55avtdkduinz68zfxhcwct80.png)
Taking the inverse function both sides,
![\begin{gathered} \angle BCA=\tan ^(-1)(2.25) \\ \angle BCA\approx66^(\circ) \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/n3awa0m5e6hma7sfdgs7tp7vy0x11lr8q4.png)
Thus, the required angle of elevation is approximately 66 degrees.