Anyone here good in trig?

1105 · May 2, 2005

Need some help with solving trig equations and giving all solutions... My professor is very smart, but completly stupid when it comes to teaching the material so I need some help... Please only people who know what they are doing... No BSing since this is for a grade.

2cos^2(x)-1=0

tan(x)sin(x)+sin(x)=0

2sin^2(x)-sin(x)=1

illwood · May 2, 2005

I think I can probably help you out.

First off, what can you use for Trig Identities?
Trig Identities

At the bottom of the page, you can see that most things are substitution and simplification.

Synned · May 2, 2005

Jeezus christ I just had a major test on ****ing identites. They suck major ass.
We didn't have to do things like that, just prove that they were equal. Like
1-sin = csc or some **** like that.

Scot_94GT · May 2, 2005

1105 said:
Need some help with solving trig equations and giving all solutions... My professor is very smart, but completly stupid when it comes to teaching the material so I need some help... Please only people who know what they are doing... No BSing since this is for a grade.

2cos^2(x)-1=0

2cos^2(x) = -1

cos^2(x) = -1/2

cos(x) = -1/root2

x = -PI/4

1105 said:
tan(x)sin(x)+sin(x)=0

tan(x)sin(x) = -sin(x)

tan(x) = -1

x = -PI/4

1105 said:
2sin^2(x)-sin(x)=1

2sin(x) - 1 = 1/sin(x)

forgot my trig identities

1105 · May 2, 2005

proving idenities sucks, but solving for them is a whole different story Scot, thanks for the help

when finding the magnitude of vector 4+3i, the answer the square root of (16-9) right?

1105 · May 2, 2005

Do you know of any ways to input it into a TI89 and have it solve for x?

VibrantRedGT · May 2, 2005

Trig Newtons rule! Now I want some.

Venom351R · May 2, 2005

VibrantRedGT said:
Trig Newtons rule! Now I want some.

1105 · May 2, 2005

you guys are such great help

Scot_94GT · May 2, 2005

1105 said:
when finding the magnitude of vector 4+3i, the answer the square root of (16-9) right?

hmmm.. I remember vetors (in physics type classes) having an i,j, and k component...referring to the x,y and z axes respectively. So if the vector was 4i + 3j, then the magnitude would be root(16+9). So I'm not sure where the 4+3i is coming in...unless they are talking about real and imaginary numbers...where the real numbers are the x axis, and the imaginary numbers are the y axis...in which case the magnitude of 4+3i would be root(16+9).

Venom351R · May 2, 2005

1105 said:
you guys are such great help

95Mustang302 · May 2, 2005

god I hated trig, but not as much as I hate calc, I'm struggling to get a C in that class right now and it blows!!

Nagash01WS6 · May 2, 2005

Scot_94GT said:
2cos^2(x) = -1

2cos^2(x)-1=0
cos^2(x) = -1/2
cos(x) = -1/root2
x = -PI/4

Should be +pi/4
2cos^2(x)-1=0
2cos^2(x)=1
cos^2(x)=(1/2)
cos(x)=+-(1/sqrt(2))
x=pi/4, 3pi/4, 5pi/4, 7pi/4

tan(x)sin(x) = -sin(x)
tan(x) = -1
x = -PI/4 AKA 7pi/4

I agree

2sin(x) - 1 = 1/sin(x)
forgot my trig identities

Factor it.
2sin^2(x)-sin(x)=1
2sin^2(x)-sin(x)-1=0
(2sin(x)+1)(sin(x)-1)=0
2sin(x)+1=0
sin(x)=-(1/2)
x=7pi/6, 11pi/6
sin(x)-1=0
sin(x)=1
x=pi/2

Nagash01WS6 · May 2, 2005

Its the trig math off here on Stangnet tonight.

1105 · May 2, 2005

let it continue

modulus of z=-3+5i... would that be squareroot of ( -3squared + 5squared)?

write the complex numbers in trigonometric form with argument theta between 0 and 2pi

-12i

4(squareroot(3-4i))

Scot_94GT · May 2, 2005

1105 said:
let it continue

modulus of z=-3+5i... would that be squareroot of ( -3squared + 5squared)?

write the complex numbers in trigonometric form with argument theta between 0 and 2pi

-12i

4(squareroot(3-4i))

That's it I'm out.
Let me know when you get to calculus...at least that stuff is useful.

1105 · May 2, 2005

give me a few more weeks then. My trig final is thursday, takingsummer off, then calc 1 and physics in fall

Nagash01WS6 · May 2, 2005

Calc is easy compared to the end of trig. All this stuff is BS and I have yet to use it.

1105 · May 2, 2005

that makes me feel better about life... seriously it does

donjohn · May 2, 2005

Nagash01WS6, has his **** down, except for the potential value of this stuff, depending on your major... now i'm only lower division electrical engineering but we use this stuff all the time

1105, when you need the magnitude, you take the square root of both the x^2 + y^2 variables: so magnitude of vector 4+3i = 5 bc sqrt(4^2 + 3^2) = sqrt25 = 5

Anyone here good in trig?

1105

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