# Homework Help: Trigonometry Problem Solving Question

1. May 25, 2013

### Zashmar

Question:
"A cat sitting on the edge of a straight river bank spots a bird sitting in a tree directly across the river's edge. The angle of elevation from the cat to the bird is 15°. The cat the moves 25m along the river bank, and now spots the same bird at an angle of elevation of 13°. How high is the tree?

There is not enough information to do this, that is why it asks for assumptions.

I have drawn the diagram, and then realised there are not enough angles or sides to work it out. I then thought that i would have to ASSUME THAT THE TRIANGLE FORMED FROM THE CAT WALKING 25m WAS A RIGHT ANGLED TRIANGLE.

However when i then calculate the size of the tree not only is the answer wrong, but for each sub-viewing-traingle i found a different value of the size of the tree. The answer in the book says that the tree is 11.37m tall.

How did they get there?

2. May 25, 2013

### LCKurtz

Show us what you did and what answer you got.

3. May 25, 2013

### ehild

Hi Zashmar,

How did you get to the wrong solution? Show your work.

A picture can help. I show you one. You are right, there are right triangles- one horizontal, as initially, the cat sits opposite to the tree, then walks 25 m along the tree. The other triangles are vertical. Write up all equations for the unknowns: hight of tree (h), width of the river (w) distance from the tree (d) after the cat walked 25 m.

ehild

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• ###### cattree.JPG
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Last edited: May 26, 2013