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#1 2005-07-23 23:10:22
- GurraTedden
- Member
- Registered: 2005-07-20
- Posts: 19
Angle equation
Hi.
How do I solve sin(θ) = 0.38cos(θ) ???
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#2 2005-07-23 23:14:32
- MathsIsFun
- Administrator
- Registered: 2005-01-21
- Posts: 7,713
Re: Angle equation
I remember my trig using "SOHCAHTOA" (see http://www.mathsisfun.com/sine-cosine-tangent.html)
Therefore tan θ = sin θ / cos θ
So: sin(θ)/cos(θ) = 0.38 = tan θ
And: θ = tan-¹ 0.38 = 20.8°
"The physicists defer only to mathematicians, and the mathematicians defer only to God ..." - Leon M. Lederman
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#3 2005-07-23 23:17:40
- mathsyperson
- Moderator
- Registered: 2005-06-22
- Posts: 4,900
Re: Angle equation
Divide both sides by cosθ: sinθ/cosθ=0.38
Simplify left-hand side: tanθ=0.38
Take arctans: θ=tan-¹(0.38)=20.8° to 1 decimal place
Why did the vector cross the road?
It wanted to be normal.
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#4 2005-07-23 23:19:36
- MathsIsFun
- Administrator
- Registered: 2005-01-21
- Posts: 7,713
Re: Angle equation
SNAP 
(Looking at the times, I must be slower at finishing my posts)
"The physicists defer only to mathematicians, and the mathematicians defer only to God ..." - Leon M. Lederman
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#5 2005-07-23 23:37:30
- mathsyperson
- Moderator
- Registered: 2005-06-22
- Posts: 4,900
Re: Angle equation
You can time how long it takes people to post?
That's extremely cool/pointless.
Why did the vector cross the road?
It wanted to be normal.
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#6 2005-07-24 00:00:01
- MathsIsFun
- Administrator
- Registered: 2005-01-21
- Posts: 7,713
Re: Angle equation
No, not really, though that is an interesting idea. It just seemed to me that there were 3 minutes difference between our posts, but I started first, but . . . oh, I don't know!
"The physicists defer only to mathematicians, and the mathematicians defer only to God ..." - Leon M. Lederman
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#7 2005-07-24 00:23:28
- Zach
- Member
- Registered: 2005-03-23
- Posts: 2,075
Re: Angle equation
Failure.
Boy let me tell you what:
I bet you didn't know it, but I'm a fiddle player too.
And if you'd care to take a dare, I'll make a bet with you.
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#8 2005-07-27 21:43:10
- Nitrofu
- Guest
Re: Angle equation
the 3d .obj reader i have at http://www15.brinkster.com/nitrofurano/sdlbasic/ uses this
(i needed to rotate the viewer over the landscape, and for this i need to know the angle)
(this is simple to do as code, i don't know math notations as well...)
#9 2005-07-27 21:46:40
- Nitrofu
- Guest
Re: Angle equation
the problem starts when (using arcsin, arccos and arctan) you need to know the quadrant for angles larger than 90degrees (afaik)
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