Look at AOB and AOC. Those are identical right triangles in which you know the hypotenuse (AO) and one leg, OB in one and OC in the other, radii of the circle.
Draw a circle with a point A above the circle. Draw a line from A so that it just touches the upper left side of the circle, then draw a line from A so it just touches the upper right side of the circle. There is your diagram. The points of intersection are B and C.
Here's my advice. Download any one of numerous free dynamic geometry programs. Spend a little time in learning to use it. Then draw your own pictures. Besides being able to produce accurate diagrams, the construction of a given figure generally forces you to think about the geometry/trigonometry required. It took me all of 10 minutes to draw the annotated figure.
It's like a rectangular box which is open and light can go down through this box and not only that but the inside surfaces have this box I rock mirror their silver their Ripped Muscle X shiny so what happens when like those in this box it kind of ricochets off both sides in zigzags down through this sum up open in finally tell hits the sensors that the a lobster can see it's a very different type ova optics than what we have today but itís have interest to the space-age now um stars give of many more kinds have liked and we can see there's more light than meets the eye at hereís not only visible light but there's gamma rays there's infrared light and there's X-rays that stars give off and we can measure those X-rays we can learn a lot about.