The diagram shows rays of light from a point source, P, that reach a detector, D, along two paths. One path is a straight line, while the other is bent by reflection off a mirror. What is the value of b, correct to one decimal place? Assume that all the points in the diagram lie in the same plane.

Question

anonymous · Answer

attachment

anonymous · Answer

5.4

4.2

3.6 

2.8

danjs · Answer

law of sines or cosines can be used

danjs · Answer

you know the angles at P and D are equal because the legs of the triangle opposite are equal

danjs · Answer

so

$$\frac{ 180 - 112.62 }{ 2 }$$

danjs · Answer

sin(33.69)/b = sin(112.62)/6

ganpat · Answer

Sine rule says.. 

SinA/a = SinB/b = SInC/C

and put values derived from @DanJS  formula..

danjs · Answer

b = 3.6

anonymous · Answer

I understood that better from you guys than the actual lesson itself, thank you

danjs · Answer

ha, no prob