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trying to understand how pairs of angles work? watch

1. E.g in this question i have to resolve the P into perpendicular and parallel to the inclined plane, but then how would i work out the angle it has? Does it have something to do with complementary or congruent angles? Does anyone have a good resource for this pair of angles BS as well? Sorry for the anger
2. It might help to sort out the BS if you consider that COsine stands for complementary sine. In other words it COsine is the sine of 90-the angle.

In an particular force resolving situation, you can use sine or COsine or both.

Starting from the rather pithy response from b9710 we can resolve P parallel to the plane as P as P cos 20 or P sin 70. Similarly to illustrate the point the horizontal component of F is either Fcos 20 or F sin 70.

If you are taking notes off a teacher, they might be inconsistent in whether they use sin or cos in a particular situation from question to question. The thing is you could do all the resolving using cos or all the resolving using sin. Most people use sin for one component and cos for the other with the same angle. You could use sin for both and use (in this case) P cos 20 for parallel to the plane and P cos 70 for perpendicular to the plane. OR you could use P sin 70 for parallel to the plane and P sin 20 for perpendicular to be plane.

In this case, MOST people would use P cos 20 for parallel to the plane and P sin 20 for perpendicular to the plane.
3. (Original post by nerak99)
It might help to sort out the BS if you consider that COsine stands for complementary sine. In other words it COsine is the sine of 90-the angle.

In an particular force resolving situation, you can use sine or COsine or both.

Starting from the rather pithy response from b9710 we can resolve P parallel to the plane as P as P cos 20 or P sin 70. Similarly to illustrate the point the horizontal component of F is either Fcos 20 or F sin 70.

If you are taking notes off a teacher, they might be inconsistent in whether they use sin or cos in a particular situation from question to question. The thing is you could do all the resolving using cos or all the resolving using sin. Most people use sin for one component and cos for the other with the same angle. You could use sin for both and use (in this case) P cos 20 for parallel to the plane and P cos 70 for perpendicular to the plane. OR you could use P sin 70 for parallel to the plane and P sin 20 for perpendicular to be plane.

In this case, MOST people would use P cos 20 for parallel to the plane and P sin 20 for perpendicular to the plane.
I understand that to find the component opposite the angle it would be sin, but what i'm confused about is how you actually find the value of the angle, like how do you know which angle is 20 degrees once i've resolved it into a vector triangle.
4. Essentially, that is all a case of using parallel lines to work out the adjacent and corresponding angles.
5. (Original post by ErniePicks)

E.g in this question i have to resolve the P into perpendicular and parallel to the inclined plane, but then how would i work out the angle it has? Does it have something to do with complementary or congruent angles? Does anyone have a good resource for this pair of angles BS as well? Sorry for the anger
6. (Original post by thefatone)
you are a sex god, thank you.

Do you know why the angle arrowed theta in the smaller triangle is the same as angle theta in the larger triangle?
7. (Original post by ErniePicks)
you are a sex god, thank you.

Do you know why the angle arrowed theta in the smaller triangle is the same as angle theta in the larger triangle?

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