Hi, I’m tuck on a proving trig question Watch

Onlyasking
Badges: 12
Rep:
?
#1
Report Thread starter 1 month ago
#1
1- cos2x / cos^2 = tan^2 x
Posted on the TSR App. Download from Apple or Google Play
0
reply
esrever
Badges: 20
Rep:
?
#2
Report 1 month ago
#2
Probably tan^2 x + 1 = sec^2 x is useful
Posted on the TSR App. Download from Apple or Google Play
0
reply
BobbJo
Badges: 12
Rep:
?
#3
Report 1 month ago
#3
use cos 2x = 2 cos^2 x -1
then simplify the fraction and use a pythagorean identity
0
reply
begbie68
Badges: 16
Rep:
?
#4
Report 1 month ago
#4
or simply cos2x = 1 - sin^2 x
?!
0
reply
BobbJo
Badges: 12
Rep:
?
#5
Report 1 month ago
#5
(Original post by begbie68)
or simply cos2x = 1 - sin^2 x
?!
um cos 2x = 1 - 2sin^2 x but okay
0
reply
begbie68
Badges: 16
Rep:
?
#6
Report 1 month ago
#6
(Original post by BobbJo)
um cos 2x = 1 - 2sin^2 x but okay
ohhhhhh so you mean there's a mishtake in the OP question, too?

should be:
... = 2tan^2(x) ?
0
reply
BobbJo
Badges: 12
Rep:
?
#7
Report 1 month ago
#7
(Original post by begbie68)
ohhhhhh so you mean there's a mishtake in the OP question, too?

should be:
... = 2tan^2(x) ?
no the OP question is correct

Spoiler:
Show
1 - cos2x/cos^2x= 1 - (2cos^2 x -1)/cos^2 x = 1 - [2 - sec^2x] = sec^2 x -1 = tan^2 x
0
reply
begbie68
Badges: 16
Rep:
?
#8
Report 1 month ago
#8
(Original post by BobbJo)
no the OP question is correct

Spoiler:
Show


1 - cos2x/cos^2x= 1 - (2cos^2 x -1)/cos^2 x = 1 - [2 - sec^2x] = sec^2 x -1 = tan^2 x

ok. cheers. I read it as
(1-cos2x)/cos^2(x) = 2sin^2(x) / cos^2(x) = 2tan^2(x)

I'm gonna have to practice LaTex to stop getting confused with some of these types of trigs involving squares and doubles....
0
reply
X

Quick Reply

Attached files
Write a reply...
Reply
new posts
Latest
My Feed

See more of what you like on
The Student Room

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

Personalise

University open days

  • University of East Anglia
    All Departments Open 13:00-17:00. Find out more about our diverse range of subject areas and career progression in the Arts & Humanities, Social Sciences, Medicine & Health Sciences, and the Sciences. Postgraduate
    Wed, 30 Jan '19
  • Aston University
    Postgraduate Open Day Postgraduate
    Wed, 30 Jan '19
  • Solent University
    Careers in maritime Undergraduate
    Sat, 2 Feb '19

Brexit: Given the chance now, would you vote leave or remain?

Remain (868)
80.07%
Leave (216)
19.93%

Watched Threads

View All