Head First 2D Geometry

you are here 4 175

triangle properties

100m will do, but can you rent the 60

o

speaker?

The 60º speakers are way cheaper but are they going to do the job?

Will everybody in the festival be able to hear or will people at the

sides be straining to hear?

That all depends on the angle of your venue. The speakers project

sound in the shape of an isosceles triangle. Your venue is also an

isosceles triangle. If the venue angle is less than 60º, then it’s all good.

Because 60º are the narrowest speakers available, it doesn’t really

matter what that angle is, as long as it’s less than 60º. If it’s more than

60º, then you’ll need to find an extra $1,000 for the 90º speakers.

Check any you think are true and that will help you find the

angle you need (it can be more than one).

Uh, yeah. Did

you notice that the

venue diagrams don’t

HAVE angles?

That’s true.

The only thing you know about the venue is the side

lengths and height (you worked out the perimeter and area

earlier, too, but they don’t tell you the angles either). Is that

enough to help you work out if the 60º speaker will do?

Sides and angles change together.

From sides you can find angles accurately.

From sides you can sometimes find angles accurately, and sometimes find them roughly.

Sides and angles change separately.

Sides tell you nothing about angles.

Is this angle less

than

60º

?

Field B

176 Chapter 4

sides and heights help ...