Before You Begin
Question #40883
The Question
A point in 3D space is projected onto the -plane to obtain the point . The coordinates of are represented by the complex number . is rotated about the origin in the complex plane by an angle to obtain the complex number , where and denotes the principal argument of such that . A new point in 3D space is formed such that its projection on the -plane corresponds to and its -coordinate is the same as that of . If is the origin, find the value of .
Options
- A.
28
- B.
60
- C.
48
- D.
32
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Monster
Ultra-high difficulty questions designed to test your limit, stamina, and deep conceptual understanding.
Concepts Behind This Question
Projection vs. Coordinate|Euler's Form and Rotations|Argument and Principal Value
Why This Question Is Tricky
Common Mistakes
This question tests the student's ability to correctly handle the principal value of the argument of a complex number before applying scalar multiplications (like halving the angle) in rotation transformations.
The trap lies in calculating using the properties of arguments: .
If a student fails to reduce this to the principal branch before dividing by 2, they will incorrectly use instead of the correct .
This leads to a completely different rotated coordinate , resulting in the incorrect point and the trap answer of 60.
Quick Facts About This Question
Question Information
| Subject | Mathematics |
| Chapter | Introduction to Three-dimensional Geometry - Class 11 |
| Concept | Projection vs. Coordinate |
| Difficulty | 8 |
| Cognitive Load | 7 |
| Target Solve Time | 160 sec |
| Access | Free |