A community for students.
Here's the question you clicked on:
 0 viewing
anonymous
 one year ago
1+cos(18x)=_____.
a) 2sin^2 (18x)
b) 2cos^2 (9x)
c) 2cos^2 (18x)
d) 2sin^2 (9x)
anonymous
 one year ago
1+cos(18x)=_____. a) 2sin^2 (18x) b) 2cos^2 (9x) c) 2cos^2 (18x) d) 2sin^2 (9x)

This Question is Closed

jim_thompson5910
 one year ago
Best ResponseYou've already chosen the best response.2\[\Large 1 + \cos(18x) = 1 + \cos(2*9x)\] \[\Large 1 + \cos(18x) = 1 + 2\cos^2(9x)  1\] \[\Large 1 + \cos(18x) = 2\cos^2(9x)\] On step 2, I used this identity \[\Large \cos(2x) = \cos^2(x)  1\] see this link for more trig identities http://tutorial.math.lamar.edu/pdf/Trig_Cheat_Sheet.pdf specifically see page 2 and the "Double Angle Formulas" section

jim_thompson5910
 one year ago
Best ResponseYou've already chosen the best response.2oops I made a typo, I meant to say \[\Large \cos(2x) = 2\cos^2(x)  1\]

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0how do i use that equation to find the answer

jim_thompson5910
 one year ago
Best ResponseYou've already chosen the best response.2I practically gave you the answer. Read through my steps again.

jim_thompson5910
 one year ago
Best ResponseYou've already chosen the best response.2You use the identity to replace cos(2*9x) with 2*cos^2(9x)  1 the "9x" is thought of as the theta in \[\Large \cos(2\theta) = 2\cos^2(\theta)  1\]
Ask your own question
Sign UpFind more explanations on OpenStudy
Your question is ready. Sign up for free to start getting answers.
spraguer
(Moderator)
5
→ View Detailed Profile
is replying to Can someone tell me what button the professor is hitting...
23
 Teamwork 19 Teammate
 Problem Solving 19 Hero
 Engagement 19 Mad Hatter
 You have blocked this person.
 ✔ You're a fan Checking fan status...
Thanks for being so helpful in mathematics. If you are getting quality help, make sure you spread the word about OpenStudy.