ACtE04 · Chapter 4Computer Organization & Embedded Systems🏛️ Past Licensure QuestionID: 464bca35

In engineering drawing and descriptive geometry, what is the exact ratio of the isometric projection length to the true length?

Multiple Choice Options

A
0.141
B
0.372
C
0.816 (or √2 / √3)
✓ Correct Option
D
0.642

Detailed Technical Solution & Explanation

In an isometric projection, the object is tilted such that the three mutually perpendicular coordinate axes make equal angles ( $120^\circ$ on the plane, tilted at $\approx 35^\circ 16'$ to the projection plane). The foreshortening factor of all isometric lines is:

\text{Isometric Ratio} = \frac{\text{Isometric Length}}{\text{True Length}} = \frac{\cos(45^\circ)}{\cos(30^\circ)} = \frac{1/\sqrt{2}}{\sqrt{3}/2} = \sqrt{\frac{2}{3}} \approx 0.8165 \approx 81.65\%

This standard foreshortening ratio is conventionally rounded to 0.816 (or 0.815 in approximate tables).

Option Analysis:

•

Option A (0.141): Incorrect calculation.

•

Option B (0.372): Incorrect calculation.

•

Option C (0.816 (or √2 / √3)): Correct; standard isometric foreshortening ratio

\sqrt{2/3} \approx 0.816

•

Option D (0.642): Incorrect.

Reference: Mock Test 03NEC Licensure Syllabus

In engineering drawing and descriptive geometry, what is the exact ratio of the isometric projection length to the true length?

Multiple Choice Options

Detailed Technical Solution & Explanation

Option Analysis:

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In engineering drawing and descriptive geometry, what is the exact ratio of the isometric projection length to the true length?

Multiple Choice Options

Detailed Technical Solution & Explanation

Option Analysis:

Want to practice this topic interactively?