Find the area of the triangle formed by the lines `y-x=0,x+y=0`and `x-k=0`.

Explanation

To find the area of the triangle formed by the lines \( y - x = 0 \), \( x + y = 0 \), and \( x - k = 0 \), we will follow these steps:

### Step 1: Identify the equations of the lines
The equations of the lines are:
1. \( y - x = 0 \) (or \( y = x \))
2. \( x + y = 0 \) (or \( y = -x \))
3. \( x - k = 0 \) (or \( x = k \))

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