00:03
Okay, this is problem number 23, and it says that a bridge over a river has the shape of a circular arc.
00:20
The span of the bridge is 24 meters.
00:23
The span is the length of the cord of the arc.
00:26
The midpoint of the arc is four meters higher than the endpoints.
00:31
What is the radius of the circle that contains the arc? so if we look at this, we're going to label some points here.
00:45
We're going to make this a.
00:48
We're going to have this one b and this will be c and this one here is going to be d.
00:57
We know that oc and oa are radius.
01:19
We also know that oc is going to split ab in half.
01:26
So that means that ad equals db.
01:31
And they said that the span, they said that the span, which is ab equals 24.
01:45
So that means ad and db are 12.
01:51
So this one's 12 and this one's 12...