# Observer

The observer sees straight fence 100 m long in 30° view angle. From one end of the fence is 153 m.

How far is it from the another end of the fence?

Result

x =  179.9 m

#### Solution:

$\frac{ \sin \beta} { \sin 30^\circ } = \frac{ 153 } { 90 } \ \\ \beta = \arcsin ( \frac{ 153 } { 90 } \cdot \sin 30^\circ ) = 1.016 = 58^\circ 12'42" \ \\ \gamma = 180^\circ - 30^\circ - 58^\circ 12'42" = 91^\circ 47'18" \ \\ \ \\ \frac{ \sin \gamma} { \sin \beta } = \frac{ x } { 153 } \ \\ x = 153 \cdot \frac{ \sin \gamma} { \sin \beta } = 179.9 \ \text { m }$

Try calculation via our triangle calculator.

Leave us a comment of this math problem and its solution (i.e. if it is still somewhat unclear...):