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02072012, 06:19 PM  #1 (permalink) 
Partying on the inside
Join Date: Mar 2009
Posts: 5,584

Help me study for my physics test tomorrow!
College. Intro to Physics. I'm supposed to be studying right now, but since I have absolutely no background in trig, some steps are a bit "wut". I know how to identify the sides of a right triangle, so that's a check.
I know "soh cah toa" now, so that's also a check. Unfortunately, I've forgotten (or never got to the point where I understood) what exactly I'm using sine, cosine, tangent, and the inverses for. I understand that sin = o/h, and cos = a/h, and tan = o/a. Check. But if I have a right triangle and wish to find a side that isn't theta, am I supposed to be solving for one of the variables in o/h, a/h, or o/a? I assume I am, seeing as how if you already have 2 sides, you get the third with P. Theorem. Now help me put this in perspective. Let's say I have a right triangle whose angle is 20 degrees, and whose opposite side is 10 units. To solve for the adjacent side, I assume I would use the tangent function. So that would be 10/A (where A is the variable of the adjacent side), times the tangent of 20 degrees. Right? So where do I go from here? I can't rightly multiply a fraction with a variable as the denominator, so do I multiply both sides by the denominator to end up with just 10, and multiply 10 times the tangent of 20 degrees? I would end up with roughly 3.63 as the value of the adjacent side. Is this correct? Let me know. MORE TO COME. for real.
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02072012, 06:25 PM  #2 (permalink) 
SOPHIE FOREVER
Join Date: Aug 2011
Location: East of the Southern North American West
Posts: 35,541

Yes, that is correct. I'm only really good at the trig, so someone else is going to have to tell you about the physics application.
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Studies show that when a given norm is changed in the face of the unchanging, the remaining contradictions will parallel the truth. 
02072012, 06:28 PM  #3 (permalink) 
Music Addict
Join Date: Mar 2009
Posts: 1,711

It's been a while, so take my response with a grain of salt. I think that:
1. Setting up the equation tan(20) = 10 / A 2. Multiply both sides by denominator: A*tan(20) = 10 3. Divide both sides by tan(20): A = 10 / tan(20) 4. Simplified: A = 4.46995109 Eh? We got different answers? Well ignore mine, I haven't taken calculus in forever. 
02072012, 06:31 PM  #4 (permalink) 
SOPHIE FOREVER
Join Date: Aug 2011
Location: East of the Southern North American West
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I should've shown my work on paper, Tuna's is right.
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Studies show that when a given norm is changed in the face of the unchanging, the remaining contradictions will parallel the truth. 
02072012, 06:55 PM  #8 (permalink) 
Partying on the inside
Join Date: Mar 2009
Posts: 5,584

Ok. Let me do a problem to make sure I got it, but with the variable in the numerator.
Theta = 45 degrees Hypoteneus = 12 units. Find opposite. Sin(45) = O/12 .70 = O/12 (12).70 = O O = 8.4 Is that right?
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02072012, 06:59 PM  #9 (permalink) 
SOPHIE FOREVER
Join Date: Aug 2011
Location: East of the Southern North American West
Posts: 35,541

Correct.
EDIT: If you understand the principle of sohcahtoa, you'll be able to apply that correctly, it's just the Algebra where most people screw up the solution.
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Studies show that when a given norm is changed in the face of the unchanging, the remaining contradictions will parallel the truth. 
02072012, 07:02 PM  #10 (permalink) 
Partying on the inside
Join Date: Mar 2009
Posts: 5,584

Word. Ok. So I have the basics. Now, when doing 2 dimensional kinematics, that trig comes into play, but I also have to remember some formulas. I can put those on my phone, so I'm not worried too much about it, since my phone is also my calculator, which is allowed.
So, how would you guys go about solving something like this (taken from a homework problem): A projectile is launched from and returns to ground level. Air resistance is absent. The horizontal range of the projectile is R = 175 m, and the horizontal component of the launch velocity is Vox = 25 m/s. Find the vertical component Voy of the launch velocity.
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