# How to solve for angle of reflection in respect to floor?

1. Apr 23, 2016

### AngelLegs

1. The problem statement, all variables and given/known data
A student stands 2.7 m in front of a floor-to-ceiling mirror. Her eyes are 1.64 m above the floor and she holds a flashlight at a distance 0.85 m above he floor.
Calculate the angle θ, in degrees, that the flashlight makes with respect to the floor if the light is reflected into her eyes.

2. Relevant equations
tangent
sine

3. The attempt at a solution
I'll use inverse tangent (1.64m/2.7m) to find the angle, but I'm not sure how to set it up. I'm confused about which angle I'm finding when I use that, and which "triangle" I'm supposed to be solving for, because the light ray makes a triangle when it reflects off the mirror, and the light makes another when it reflects into the students eyes. But I'm having huge complications with figuring which ones to apply to the problem solving process.

2. Apr 23, 2016

### phinds

Draw a diagram. Also, please don't use HUGE bold print. It's unnecessary and some of us view it as obnoxious, like screaming your question.

3. Apr 23, 2016

### AngelLegs

I'm sorry, I'm new
I don't quite know how to use this website yet
Can you see the photo I posted?

#### Attached Files:

• ###### diagram.png
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4. Apr 23, 2016

### phinds

Yes. I think you have errors in your drawing in that not everything conforms to your problem statement. Another issue is that you don't know the distance of the light from the torso, so you must assume it to be zero (light is being held by side, not out front).

Get the drawing to exactly conform to the problem statement and you then have everything needed to solve this trivial problem.

5. Apr 23, 2016

### AngelLegs

I'm afraid I'm not understanding what you mean.
Is it like this?

#### Attached Files:

• ###### diagram.png
File size:
13 KB
Views:
89
6. Apr 23, 2016

### phinds

You're getting the idea. I know you have the right idea but do you really think this is an accurate model of the problem? Why does the light not line up with the stated distance. Stop drawing a stick figure and just draw the geometry.