- #1
influx
- 162
- 1
This is a screenshot from my lecture notes provided by my lecturer. He says theta=-30 and then proceeds to use a value of theta=60? Surely this is wrong?
Is this a mistake? (Stress Plane transformations)
- Thread starter influx
- Start date
-
- Tags
- Mistake Plane Transformations
Click For Summary
Discussion Overview
The discussion revolves around a potential mistake in lecture notes regarding stress plane transformations, specifically focusing on the use of angles in trigonometric functions. Participants are examining the implications of using different values for theta in the equations presented.
Discussion Character
- Debate/contested
Main Points Raised
- One participant questions the use of theta=60 when the lecturer stated theta=-30, suggesting this is a mistake.
- Another participant points out the presence of 2θ in the equation, implying that this might clarify the discrepancy.
- A participant reiterates their concern that the sine function should be evaluated using Sin[2(-30)] instead of Sin[2(60)], indicating confusion over the correct application of the angle.
- A later reply agrees with the initial concern and adds that there are additional errors in the evaluation, specifically that a term should have been subtracted rather than added, leading to a different numerical result.
Areas of Agreement / Disagreement
Participants express disagreement regarding the correct application of angles in the equations, with no clear consensus on the resolution of the identified mistakes.
Contextual Notes
There are unresolved assumptions regarding the definitions of the angles and the context of the equations being discussed, which may affect the interpretations of the participants.
This is a screenshot from my lecture notes provided by my lecturer. He says theta=-30 and then proceeds to use a value of theta=60? Surely this is wrong?
- #2
- 23,738
- 5,940
Did you not notice the 2θ in the equation?
- #3
influx
- 162
- 1
Chestermiller said:
I did but θ = -30 so surely he should have used Sin[2(-30)] rather than Sin[2(60)] as he's done above?
- #4
- 23,738
- 5,940
You're right! And that's not the only error there. They did evaluate the sin and cos of 60 correctly in their equation (omitting the factor of 2), but the second term should have been subtracted, rather than added (as they did). The answer should be 36.96, not 66.96.influx said:
Chet
Similar threads
Engineering
Alternating current circuit with transformer
- · Replies 12 ·
- · Replies 2 ·
- · Replies 1 ·
- · Replies 6 ·
- · Replies 1 ·
- · Replies 5 ·
- · Replies 5 ·
- · Replies 1 ·
- · Replies 3 ·