# how do i solve this using non right angle trig (1 Viewer)

#### kkk579

##### Well-Known Member
help would be greatly appreciated

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#### cossine

##### Active Member
help would be greatly appreciated
It is hard to read. It is rotated 90 degrees.

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#### Masaken

##### Active Member
help would be greatly appreciated
is there a way to solve it with non-right angled trig? Because a way I would use required just algebra and drawing your own right angled tringles (from the left end of the 18m down, and the same with the right end).

To calculate the width of the river (let's call it w), consider when it's both closed and open.
Closed: w = 2x (because x + x)
Open: using the right angled triangles you drew up and rearranging it, w = 2xcos50+ 18.
Then just sub in w into 2x, then solve the width from there

#### fx82au

##### Member
@Masaken explained it amazingly. This is a very common question, so make sure you know how to do it!

#### kkk579

##### Well-Known Member
is there a way to solve it with non-right angled trig? Because a way I would use required just algebra and drawing your own right angled tringles (from the left end of the 18m down, and the same with the right end).

To calculate the width of the river (let's call it w), consider when it's both closed and open.
Closed: w = 2x (because x + x)
Open: using the right angled triangles you drew up and rearranging it, w = 2xcos50+ 18.
Then just sub in w into 2x, then solve the width from there
ohhh okay tysm it was part of the non right angle trig section of the textbook so i just assumed it needed non right angle trig to solve it lol