#1

Need help in maths. I got given three sets of questions for homework, if anyone can figure out one of each to get me on my way (I've forgotten some basics) with full explanations I should be okay and be very happy )

1. For 0 < Θ < 360, solve

SinΘ(2SinΘ-1)=0

2. For -180 < Θ < 180, solve

(2sinΘ-1)(3sinΘ-1)=0

3. For 0 < Θ < 2pi, solve

8cos^3Θ=1

1. For 0 < Θ < 360, solve

SinΘ(2SinΘ-1)=0

2. For -180 < Θ < 180, solve

(2sinΘ-1)(3sinΘ-1)=0

3. For 0 < Θ < 2pi, solve

8cos^3Θ=1

#2

Need help in maths. I got given three sets of questions for homework, if anyone can figure out one of each to get me on my way (I've forgotten some basics) with full explanations I should be okay and be very happy )

1. For 0 < Θ < 360, solve

SinΘ(2SinΘ-1)=0

2. For -180 < Θ < 180, solve

(2sinΘ-1)(3sinΘ-1)=0

3. For 0 < Θ < 2pi, solve

8cos^3Θ=1

I can't help you, but I have a question, who actually uses these formulas irl?

#3

i'll do the first one

EDIT: hope i helped, ive got a NAB on this tomorrow

EDIT: hope i helped, ive got a NAB on this tomorrow

```
1. For 0 < Θ < 360, solve
SinΘ(2SinΘ-1)=0
SinΘ = 0 or 2SinΘ-1 = 0 find the 0's
SinΘ = 1/2 angle cant = 0 so 1/2 is only option
Sin +ve => 1st or 2nd quadrant
=> Θ = 30 or 180 - 30
=> Θ = 30 or 150
```

*Last edited by EMGs_rule at Feb 24, 2008,*

#4

I can't help you, but I have a question, who actually uses these formulas irl?

Architects/physicists often use them. TS, I'd help but we haven't done trigonometric equations yet.

#5

Architects/physicists often use them. TS, I'd help but we haven't done trigonometric equations yet.

Thank you, NONE of the math teachers in my school can tell me what they( or other high level math equations) are used for, and it ticks me off. Thanks.

#6

I can't help you, but I have a question, who actually uses these formulas irl?

Maths teachers

#7

For the first one:

SinΘ(2SinΘ-1)=0

SinΘ=0 2SinΘ-1=0

Θ= 0, 180, 360 SinΘ=1/2

Θ=30, 150

Basically, Θ= 0, 30, 150, 360

SinΘ(2SinΘ-1)=0

SinΘ=0 2SinΘ-1=0

Θ= 0, 180, 360 SinΘ=1/2

Θ=30, 150

Basically, Θ= 0, 30, 150, 360

*Last edited by con job at Feb 24, 2008,*

#8

I'll do the last one.. i'll use Ω instead of thèta 'cause I can't find it on my keyboard..

here we go..

8cos^3(Ω = 1 <->

cos^3(Ω = 1/8 <->

cos(Ω = (1/8)^(1/3) <->

Ω = arccos((1/8)^(1/3))

now you have 1 solution, but between 0 and 2∏ there are 2 solutions,

just look at the goneometric circle (if you know what it is..) the cos of an angle is the same as the cos of the negative angle, so your two solutions are:

arccos((1/8)^(1/3)) and -arccos((1/8)^(1/3)), or between 0 and 2∏: -arccos((1/8)^(1/3)) = 2∏-arccos((1/8)^(1/3))

so, there you go...

here we go..

8cos^3(Ω = 1 <->

cos^3(Ω = 1/8 <->

cos(Ω = (1/8)^(1/3) <->

Ω = arccos((1/8)^(1/3))

now you have 1 solution, but between 0 and 2∏ there are 2 solutions,

just look at the goneometric circle (if you know what it is..) the cos of an angle is the same as the cos of the negative angle, so your two solutions are:

arccos((1/8)^(1/3)) and -arccos((1/8)^(1/3)), or between 0 and 2∏: -arccos((1/8)^(1/3)) = 2∏-arccos((1/8)^(1/3))

so, there you go...

*Last edited by Future at Feb 24, 2008,*

#9

^^^^^

this guys does the sin-1 0 bit right :P

con job i mean

this guys does the sin-1 0 bit right :P

con job i mean

#10

I can't help you, but I have a question, who actually uses these formulas irl?

Math teachers.

#11

1. 12

2. 456

3. 1239424

2. 456

3. 1239424

#12

Hmm...

I need some more clarity :S

I need some more clarity :S