Two forces P and Q acting at a point are such that if P is reveserd, the direction of the resultant is turned through `90^(@)`. Prove that the magnitudes of the forces are equal.

Explanation

To solve the problem, we need to analyze the forces \( P \) and \( Q \) acting at a point and how their resultant changes when \( P \) is reversed. Let's break down the solution step by step.

### Step 1: Define the Resultant Forces
Let the resultant of forces \( P \) and \( Q \) be represented as \( R \). When both forces are acting in their original directions, the resultant can be expressed as:
\[ R = P + Q \]

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