Plus X, they all have toĪdd up to be 360 degrees so let's see, we could So this is 92 + 90 + 90 + question mark is going to be equal to 360 degrees. Since you have two of them, it's 360 degrees. Quadrilateral into two triangles, where the sum of all the interior angles of a triangle are 180 and The sum of the angles are going to add up to 360 degrees, and if you wonder where that comes from well you can divide a

So let me label this, so this is going to be a right angle and this is going to be a right angle. Perpendicular to a tangent or a radius that intersects a tangent is going to be perpendicular to it. This is to realize, that a radius is going to be

So the key insight hereĪnd there's multiple ways that you could approach This out right here and I encourage you to pause the video and figure it out on your own. So given all of that they're asking us what is the measure of angle A, so we're trying to figure So you see that the sides of angle A are parts of those tangents,Īnd points B and point C are where those tangentsĪctually sit on the circle. Line is tangent to the circle and (mumbles) and this line is also And when they say it'sĬircumscribed about circle O that means that the two sides of the angle they're segments that wouldīe part of tangent lines, so if we were to continue, so for example that right over there, that

So this is angle A right over here, we're talking about thisĪngle right over there. Told that angle A is circumscribed about circle O.

Khan academy circle geometry