Trigonometry buffs get a chance to flex their proverbial muscles...Thread.

[Varuna]

Sine2A=√2CosA

keep in mind the square root sign is only over the 2 and not the CosA.

 

[Khanczar]

ugh, trigonometry.

All i know about trigonometry is SohCahToa.
So i guess this is a little out of my league.

OR IS IT???






















Yeah, it is.

 

[GoldShadow]

A is pi/4 (or 3pi/4), easy.

Just need to know the double angle formula: sin(2x)=2sin(x)cos(x).

Then that means: sqrt(2)cos(x)=2sin(x)cos(x). Divide both sides by cos(x) and 2 and you have:
sqrt(2)/2=sin(x), which means that x is obviously pi/4.

 

[SonicZeroX]

A = 45

Amirite?

 

[#HBC | FrozeηFlame]

Yeah Shadow got it. Double angle identities FTW!

 

[GoldShadow]

In degrees, yes, soniczero. Same as pi/4 radians, which is what you usually give your answer in.

 

[SonicZeroX]

In degrees, yes, soniczero. Same as pi/4 radians, which is what you usually give your answer in.

Oh yea I totally forgot about that. :/

 

[Virgilijus]

A equals 45 degrees or pi/4 radians:

sin2A=2sinAcosA-->

2sinAcosA=(2^.5)cosA-->sinA=1/radical 2, A equals 45degrees.

EDIT: STUPID COMPUTER LAG!

 

[Varuna]

I love you all

 

[h1roshi]

umm..sin to the cos to the tangent of hypotenuse squared - square root of 2(xcos0............fvck it, i have no idea what i'm talking about. i just wanted to fit in...peace

-hiroshi

 

[Cyphus]

i took trig last semester at college........got a B.....and nope, can't say i remember a single **** thing. No point in me remembering how to even do all that stuff

 

[Doraki]

You all forgot A = pi/2 and A = -pi/2.

 

[Scav]

Trigonometry is witchcraft!

WITCHES!

 

[Virgilijus]

You all forgot A = pi/2 and A = -pi/2.

Actually, the complete answer is + or - n(pi)/4, n=1, 2, 3, 6 and for every subsequent revolution. But pi/4, being the first answer, is generally acceptable as the correct numeric answer (from most teacher's viewpoints).

And Scav, trigonometry is just a red herring

 

[GoldShadow]

You all forgot A = pi/2 and A = -pi/2.

Actually I said that in my first post

 

[Doraki]

Actually, the complete answer is + or - n(pi)/4, n=1, 2, 3, 6 and for every subsequent revolution. But pi/4, being the first answer, is generally acceptable as the correct numeric answer (from most teacher's viewpoints).

And Scav, trigonometry is just a red herring

why did you say "+ or -" ? You wanted to write something wrong ?
-pi/4 isn't a solution.

Goldshadow you only said pi/4 and 3pi/4, but you didn't say anything about pi/2 and -pi/2 when you divided by cos x.

... the solutions of the equation are pi/4, pi/2, 3pi/4 and 3pi/2 mod. 2pi.
A normal teacher wouldn't accept any other answer.

 

[h1roshi]

^^ who cares?

 

[Virgilijus]

why did you say "+ or -" ?

Whoops! Guess that's just habit

... the solutions of the equation are pi/4, pi/2, 3pi/4 and 3pi/2 mod. 2pi.
A normal teacher wouldn't accept any other answer.

Math teachers; yes. Physics or engineering teachers; not always so.

 

[McCloud]

I always hated the trig part of calculus.

..

angles are the devil.

But as long as we're doing math...

An object is moving along a curve with position (x(t), y(t)) on the interval 0 < or equal to t < or equal to 3. dx/dt = cos (t^3) and dy/dt = 3sin (t^2). At t = 2, the object's position is (4,5).

Find the speed of the object when t = 2.

Find the equation of the line tangent to the curve at (4,5).

I just had a test over this.

 

[GoldShadow]

why did you say "+ or -" ? You wanted to write something wrong ?
-pi/4 isn't a solution.

Goldshadow you only said pi/4 and 3pi/4, but you didn't say anything about pi/2 and -pi/2 when you divided by cos x.

... the solutions of the equation are pi/4, pi/2, 3pi/4 and 3pi/2 mod. 2pi.
A normal teacher wouldn't accept any other answer.

My bad, I misread your first post.

Also, hell, I've just been made fool of in something I'm really good at, heh. Can't believe I missed that. Doraki's right folks. Now I feel stupid.

 

[Atmuh]

sohcahtoa :]