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Old 02-07-2012, 07:02 PM   #11 (permalink)
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Ok a little heads up I noticed with the dumb google calculator

tan(20 degrees) is actually equal to 0.36, not sure why google calculator was giving me that other number. But the steps are the same. So the first answer is actually something like 27.

And yes you're answer looks right
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Old 02-07-2012, 07:05 PM   #12 (permalink)
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Oh, one more thing about trig real quick. If I want to find the angle of a right triangle, I know I need to use inverse sin, cos, or tan.

Walk me through the steps of finding the angle of a right triangle whose hypoteneus is 5 units, and whose opposite side is 7 units.
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Old 02-07-2012, 07:09 PM   #13 (permalink)
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opposite side can't be larger than the hypotenuse
. . .but if the numbers are reversed, you have

sin(x) = 5/7 = .7

x = arcsin (.7)
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Old 02-07-2012, 07:09 PM   #14 (permalink)
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Originally Posted by Freebase Dali View Post
Oh, one more thing about trig real quick. If I want to find the angle of a right triangle, I know I need to use inverse sin, cos, or tan.

Walk me through the steps of finding the angle of a right triangle whose hypoteneus is 5 units, and whose opposite side is 7 units.
I think it's as simple as arcsin(7/5). Just put that into your calculator.

It's basically just the reverse, there's no steps involved, unless it was values used on 45-45-90 triangles or 30-60-90

Plus what skaltezon said LOL
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Old 02-07-2012, 07:12 PM   #15 (permalink)
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K. Disregarding the fact that my triangle is breaking all the rules, I would simply divide the opposite side by the hypoteneus and multiply that number by the inverse of sin? That works for me.
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Old 02-07-2012, 07:12 PM   #16 (permalink)
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Quote:
Originally Posted by Freebase Dali View Post
Oh, one more thing about trig real quick. If I want to find the angle of a right triangle, I know I need to use inverse sin, cos, or tan.

Walk me through the steps of finding the angle of a right triangle whose hypoteneus is 5 units, and whose opposite side is 7 units.
Hypotenuse is always smaller than the opposite. If I recall correctly, you can plug in arcsin(7/5) in a calculator to get your answer.

edit: damn, I was too slow
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Old 02-07-2012, 07:13 PM   #17 (permalink)
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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.
I haven't taken college physics but isn't the equation just displacement = velocity * time ?
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Old 02-07-2012, 07:15 PM   #18 (permalink)
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K. Disregarding the fact that my triangle is breaking all the rules, I would simply divide the opposite side by the hypoteneus and multiply that number by the inverse of sin? That works for me.
Yes. That will give you the angle.
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Old 02-07-2012, 07:16 PM   #19 (permalink)
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I haven't taken college physics but isn't the equation just displacement = velocity * time ?
Well displacement is actually velocity over time (d = v/t) if I remember correctly, but that's one dimensional. The problem has both the x and y dimension, and is asking for the components of the vector, which the vector would be a diagonal line. I would need to figure out the x component and the y component that made the resultant vector.
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Old 02-07-2012, 07:17 PM   #20 (permalink)
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Originally Posted by Freebase Dali View Post
K. Disregarding the fact that my triangle is breaking all the rules, I would simply divide the opposite side by the hypoteneus and multiply that number by the inverse of sin? That works for me.
No. Find the value of 5/7 and look in a table to see what angle has that sine value. Or use your scientific calculator, if that's permitted.
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