Let's break down your problem and solve it step by step.

1. Draw a Right Triangle ABC

Given:

• Points $A(0.70, 20)$ and $B(60, -10.60)$
• The top vertex $C$ is horizontally aligned at $C(60, 90)$.

We can now determine the structure of triangle ABC.

1. Vertices of Triangle ABC:
   • $A(0.70, 20)$
   • $B(60, -10.60)$
   • $C(60, 90)$

This triangle is right-angled at vertex $B$, as $C$ is vertically above $B$ (same x-coordinate).

Diagram:

You can visualize this triangle, where:

• Line AB represents one side,
• Line BC is the vertical height from point $B$ to $C$,
• Line AC is the hypotenuse.

2. Find the Orthogonal Ω and Vertex D

Orthogonal Ω:

The orthogonal $\Omega$ of triangle ABC refers to the line that is perpendicular to the plane of triangle ABC.

• Since we know that $\overrightarrow{BC}$ is vertical, we can focus on the orthogonal that is perpendicular to the plane defined by the points $A, B, C$.
• The orthogonal line passes through a point in space perpendicular to the surface.

Finding Vertex D:

• $D$ forms a rectangle ABCD. Since triangle ABC is right-angled at $B$, we need to find a point $D$ such that $ABCD$ is a rectangle, and $D$ is positioned such that $D$ makes a right angle with lines $AB$ and $BC$.

We know:

• $AB$ is diagonal along the base.
• $BC$ is vertical.

Thus, $D$ is located horizontally from point $A$ and vertically aligned with $C$.

3. Find the Cross Section of the Rectangle

• The cross section refers to the intersection between the plane parallel to the rectangle and another plane.
• The plane $B1$ and a seal at 45° would define the angle for this cross-section.

Given that the plane B1 is parallel and the seal is inclined at 45°, the intersection of the ABCD rectangle with the seal will give you a section of the rectangle. You can compute the coordinates of the points of intersection by projecting along the angle of the seal.

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Would you like a more detailed breakdown of any of these points? Here are some related questions you could explore:

1. How do we calculate the lengths of sides of triangle ABC?
2. What is the area of triangle ABC?
3. How do we determine the slope of the hypotenuse $AC$?
4. How do we find the equation of the plane containing triangle ABC?
5. What does the 45° seal mean geometrically for the cross-section?

Tip:

Always start by analyzing the given points in relation to each other on the coordinate plane before solving more complex geometric properties.