For a given velocity of projection from a point on the inclined plane, the maximum range down the plane is three times the maximum range up the incline. Then find the angle of inclination of the inclined plane.

Explanation

To solve the problem, we will use the formulas for the maximum range of projectile motion on an inclined plane. Let's break down the solution step-by-step.

### Step 1: Understand the problem
We need to find the angle of inclination (θ) of the inclined plane given that the maximum range down the plane (R2) is three times the maximum range up the incline (R1).

### Step 2: Write the formulas for maximum range
The maximum range on an inclined plane can be expressed as:
- For upward projection (R1):
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