To reflect the triangle across the given mirror line, follow these steps:

1. Identify the distance from the mirror line: Measure how far each vertex (corner) of the triangle is from the red mirror line.

2. Reflect each vertex: For each vertex, measure the same distance on the opposite side of the mirror line, maintaining the perpendicular direction.

3. Draw the reflected triangle: Connect the reflected vertices to form the new triangle.

Looking at the mirror line in the image, which is diagonal, it appears to be at a 45-degree angle. This means the reflection will also maintain the shape but in a flipped orientation across the mirror line.

Do you need more detailed help on how to calculate the exact reflection? Would you like further details on any specific step?

Here are 5 related questions to expand this concept:

1. What happens to the orientation of a shape after reflection across a diagonal line?
2. How do you reflect a point across a diagonal mirror line using coordinates?
3. How can you verify the accuracy of a reflection on a grid?
4. What is the difference between reflecting a shape across a horizontal versus a diagonal line?
5. How do reflections affect symmetry in geometry?

Tip: Always ensure the distance between each point and the mirror line is identical on both sides to ensure an accurate reflection.