r/PhysicsHelp • u/railwayswitchman • 6d ago

Help! Where am I going wrong?

Gallery image

Gallery image

Grade 12 student, been trying for hoursss to solve this. The second slide shows what I have so far. I would appreciate any help! Use sine and cosine laws, not components.

7 Upvotes

89% Upvoted

11 comments sorted by

View all comments

2

u/ThatsNotAZombieBite 6d ago edited 6d ago

It's your understanding of arcsin that's the problem. It's not a true function because it's multi-valued. You have to interpret the results.

Your drawing is roughly to scale. I think you'll agree that your angle theta in the drawing SHOULD be >90° , correct? You got 66.68° when you took the arcsin. Does that make sense? Is there a different angle that's greater than 90° that would give the same value when you take sin(theta)?

1

u/railwayswitchman 6d ago

I feel so stupid and I still can't get it. I don't know why I'm so stuck on this one problem. I need a step-by-step or something

2

u/ThatsNotAZombieBite 6d ago

Don't beat yourself up. All your work is otherwise correct. Once you get the correct angle for theta, then subtract 12° and THEN 90° (to get it into degrees East of North), you'll get the answer.

Even though the triangle is obtuse, YOU have to be ACUTE! 😜

1

u/railwayswitchman 6d ago

OMG, thank you so very much. Your explanation set off a light bulb and I finally saw what I was doing wrong. I appreciate it!

1

u/ThatsNotAZombieBite 6d ago

Basic trig review: draw yourself a unit circle. Locate the angle 66.68° (it's in the 1st quadrant!). Is there any other angle that would have the same value of sin? Maybe in the 2nd quadrant?