# trig questions c4Watch

Announcements
#1
The Q is, solve the equation, Tan2X = 3Tanx for 0 to 2 Pi (interval),

Right I changed Tan 2X into the double angle identity, and took 3Tanx to the other side, I thought since its equal to 0 the bottom part of the fraction, of the double angle identity will cancel out but it dosent in the answer?

Btw the identity for tan2x is 2TanX/ 1- Tanx^2
0
3 years ago
#2
1
3 years ago
#3
(Original post by SunDun111)
The Q is, solve the equation, Tan2X = 3Tanx for 0 to 2 Pi (interval),

Right I changed Tan 2X into the double angle identity, and took 3Tanx to the other side, I thought since its equal to 0 the bottom part of the fraction, of the double angle identity will cancel out but it dosent in the answer?

Btw the identity for tan2x is 2TanX/ 1- Tanx^2

The denominator does "cancel" out when you multiply through by the denominator, but that means you need to multiply th 3 tan x by the denominator too.

The reason why works is by multiplying by the denominator.

0
#4
(Original post by Zacken)

The denominator does "cancel" out when you multiply through by the denominator, but that means you need to multiply th 3 tan x by the denominator too.

The reason why works is by multiplying by the denominator.

Yeah I figured it out that was the question and i got the answers, now im kinda stuck on another,

The question is 2 Cos x^2 = 2SinxCosx + 1

How can I do this? Do i need to factorise it so i can solve two equations?
0
3 years ago
#5
Maybe this helps: 2sinxcosx+1=(sinx+cosx)^2
0
3 years ago
#6
(Original post by SunDun111)
Yeah I figured it out that was the question and i got the answers, now im kinda stuck on another,

The question is 2 Cos x^2 = 2SinxCosx + 1

How can I do this? Do i need to factorise it so i can solve two equations?
Move the one over to the other side of the equation:

but this is precisely by using your trig identities.

Hence:
0
3 years ago
#7
(Original post by Math12345)
Maybe this helps: 2sinxcosx+1=(sinx+cosx)^2
I can't immediately see how this is helpful?
0
3 years ago
#8
(Original post by Zacken)
I can't immediately see how this is helpful?

or
or
Now solve.

0
3 years ago
#9
(Original post by Math12345)

or
or
Now solve.

I see, bit long winded but it'd do. Thanks.
0
X

new posts
Back
to top
Latest
My Feed

### Oops, nobody has postedin the last few hours.

Why not re-start the conversation?

see more

### See more of what you like onThe Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

### University open days

• University of Suffolk
Mon, 9 Dec '19
• University of Hertfordshire
Wed, 11 Dec '19
• University of Lincoln
Wed, 11 Dec '19

### Poll

Join the discussion

#### Which party will you be voting for in the General Election?

Conservatives (167)
19.26%
Labour (440)
50.75%
Liberal Democrats (117)
13.49%
Green Party (49)
5.65%
Brexit Party (13)
1.5%
Independent Group for Change (Change UK) (4)
0.46%
SNP (15)
1.73%
Plaid Cymru (4)
0.46%
Democratic Unionist Party (DUP) (0)
0%
Sinn Fein (6)
0.69%
SDLP (1)
0.12%
Ulster Unionist (4)
0.46%
UKIP (9)
1.04%
Other (7)
0.81%
None (31)
3.58%