The image contains a set of geometric diagrams and questions written in Indonesian. Here’s a breakdown of the problem:

Problem Context:

The diagrams show circles with chords, angles, and labeled points. Specifically, they seem to be related to concepts of circle geometry involving chords, angles subtended by chords, and how the angles might change based on certain conditions.

Translation of the Questions:

1. Question 1: "If a lamp is placed at the center of a pool and wants to project onto $BC$, can a lamp with a projection angle of 30° be used? If not, what angle is needed?"

   This question seems to involve projecting light onto a specific chord (BC) from a central point in the circle, requiring you to calculate the necessary projection angle for this task.

2. Question 2: "If the lamp is not placed at the center of the pool but still wants to project onto $BC$, how does the change in the location of the projection (angle $\theta$) affect the angle?"

   Here, the question is about changing the lamp's position (likely referring to point $M$) and examining how the angle of projection ($\theta$) will adjust.

3. Question 3: "If the length of the chord $BC$ changes, how will it affect the angle of projection needed?"

   This question is asking about the relationship between the length of the chord $BC$ and the angle subtended by that chord.

Would you like me to solve one of these problems or provide a step-by-step explanation of how to approach them? Feel free to clarify any specific question!

Here are some related questions to deepen your understanding:

1. What is the relationship between the angle subtended by a chord and the central angle in a circle?
2. How does the angle subtended by a chord change as you move along the circle's circumference?
3. Can you calculate the projection angle of a lamp from a central point in a circle to a specific chord using geometric principles?
4. How does the length of a chord affect the angle subtended by that chord at the center of the circle?
5. How would the position of point $M$ (from which the angle $\theta$ is measured) influence the size of the angle?

Tip: Angles subtended by the same chord are equal if they are subtended from points on the circle.