Isometric projection — angles between cube edges in the view In a true isometric projection of a cube, the projected edges are equally inclined. What is the angular separation, in degrees, between any two of the three principal axes as they appear on the drawing?

Introduction / Context:
Isometric projection is the most widely used axonometric method because it maintains equal foreshortening along all three principal axes, producing a visually balanced view suitable for technical communication.

Given Data / Assumptions:

• Equal foreshortening is applied along X, Y, and Z.
• Axes are oriented so that their projections are symmetrically spaced.
• No perspective convergence is used (parallel projection).

Concept / Approach:
In isometric projection, the three principal axes are separated by 120 degrees from one another on the drawing. This arises because the object is rotated such that the angle between any pair of projected axes is equal, forming a 120–120–120 degree triad.

Step-by-Step Solution:
Rotate the object so that each principal axis makes equal angles with the projection plane.Project the axes; they appear as three lines from a point, equally spaced.Measure the angle between any two axes on the paper; it is 120 degrees.Apply equal scale to edges along each axis to maintain isometry.

Verification / Alternative check:
Common construction uses axis directions of 30 degrees above/below the horizontal for two axes, with the vertical axis upright; the internal angles between any pair are 120 degrees.

Why Other Options Are Wrong:

• 30 or 60 degrees: these are typical angles to horizontal lines, not the inter-axis separation.
• 90 degrees: orthographic multiview axes, not isometric.

Common Pitfalls:
Confusing the 30-degree axis tilt with the 120-degree inter-axis spacing leads to misdrawn isometric grids.

Final Answer:
120