Drawing ellipses in CAD In a modern CAD system, an ellipse can be drawn by specifying which geometric information to fully define its size and orientation?

Introduction / Context:
Ellipses appear frequently in engineering graphics, especially when circles are viewed at an angle (for example, holes in isometric/oblique views). Most CAD systems provide multiple methods to construct an ellipse, but the most robust and widely taught method uses its axes definition.

Given Data / Assumptions:

• A standard CAD environment is assumed.
• The goal is to define an ellipse's size and orientation unambiguously.
• Users can enter precise coordinates or snap to geometry.

Concept / Approach:
An ellipse can be fully defined by its center point, its major axis length and direction, and its minor axis length (perpendicular to the major axis). This approach captures both size and orientation. Many CAD tools implement this by asking for center, endpoint of the major axis, and a minor axis value, or by asking for endpoints of the major axis followed by the minor radius. Unlike a circle, an ellipse cannot be defined by a single radius; it requires two semi-axes.

Step-by-Step Solution:

Verification / Alternative check:
Rotate the defined ellipse around its center in CAD: the axes lengths remain constant, confirming a true ellipse. Converting to a spline and back should yield consistent geometry if defined by axes parameters.

Why Other Options Are Wrong:

• The bounding lines: ill-defined for ellipses; not a standard CAD input.
• Midpoint and end points: insufficient unless the tool specifically interprets them as axis endpoints.
• Center and radius: a single radius defines a circle, not an ellipse.

Common Pitfalls:

• Confusing diameter with axis length; CAD often expects semi-axis values.
• Accidentally locking ortho mode and mis-orienting the major axis.

Final Answer:
The center and major and minor axes