My Math Forum  

Go Back   My Math Forum > High School Math Forum > Trigonometry

Trigonometry Trigonometry Math Forum


Reply
 
LinkBack Thread Tools Display Modes
April 23rd, 2009, 10:30 AM   #1
Newbie
 
Joined: Apr 2009

Posts: 3
Thanks: 0

Trig Interval Question

I solved each problem, so if someone can check them I would appreciate it!

1. Solve the equation in the interval [0,2pi)
tanxcosx-cosx=0
I found all solutions of the equation to be
Cos: pi/2 +2npi ; 3pi/2 + 2npi The problem is both yield error when plugging into a calc so do I just exclude? n is any integer
Tan: pi/4 +npi (this is just pi instead of 2pi because one period of tan is from (-pi/2, pi/2)

If the question asks for the solutions in the interal [0,2pi) then the answers would just be pi/4?

2. Solve the equation in the interval [0,2pi)
2 cos^2x+sinx=1

For all solutions of the above I got 7pi/6 + 2npi; 11pi/6 + 2npi; pi/2 + 2npi
So, for the interval [0,2pi] would it just be pi/2, 7pi/6, 11pi/6
kev085 is offline  
 
April 23rd, 2009, 10:42 AM   #2
Newbie
 
Joined: Apr 2009

Posts: 3
Thanks: 0

Re: Trig Interval Question

Here is some additional work for #1 and #2

1. tanxcosx-cosx=0
cosx(tanx-1)=0

cosx=0 thus x is pi/2 and 3pi/2 but when checked yields error
tanx=1 @pi/4

2. 2cos^2x+sinx=1
2(1-sin^2x)+sinx-1=0
2-2sin^2x+sinx-1=0
-2sin^2x+sinx+1=0
-1(2sinx+1)(sinx-1)=0
2sinx+1=0
sin x=-1/2 @7pi/6 and 11pi/6
sinx-1=0
sin x =1 @pi/2
kev085 is offline  
Reply

  My Math Forum > High School Math Forum > Trigonometry

Tags
interval, question, trig



Search tags for this page
Click on a term to search for related topics.
Thread Tools
Display Modes


Similar Threads
Thread Thread Starter Forum Replies Last Post
Confidence Interval question help lilyungn Advanced Statistics 0 June 20th, 2010 04:13 PM
Decreasing trig functions over interval TsAmE Calculus 7 April 29th, 2010 11:23 AM
Help with the interval question 450081592 Calculus 2 November 15th, 2009 07:23 PM
help on Confidence Interval statistical question Kat-M Advanced Statistics 0 May 12th, 2009 10:26 AM
An Interval question sampimpinthug Algebra 2 June 14th, 2008 05:05 AM





Copyright © 2019 My Math Forum. All rights reserved.