My Math Forum  

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

Algebra Pre-Algebra and Basic Algebra Math Forum

LinkBack Thread Tools Display Modes
November 19th, 2007, 03:11 PM   #1
Joined: Oct 2007

Posts: 19
Thanks: 0

challenge problems

If sin A=1/squareroot 3 with 0<A<pi/2, and cos B= -1/2squareroot3, with pi/2<B<pi, calculate

a)cos(A+B) b) sin(A+B) c) cos2A d) cos A-B)
axelle is offline  
November 19th, 2007, 03:25 PM   #2
Senior Member
Joined: May 2007

Posts: 402
Thanks: 0

Could you explain the restrictions of numbers A and B? It's like saying that two is two but is should be between 1 and 3!
milin is offline  
November 19th, 2007, 03:54 PM   #3
Joined: Nov 2007

Posts: 6
Thanks: 0

If sin A= 1/√3 with 0<A<pi/2, and cos B= -1/2√3, with pi/2<B<pi, calculate...

I hope that this is clearer to read. Just in case, it says sin A= 1 over squareroot 3 with 0 is less than A and less than pi over 2, and cos B= negative one over 2 squareroot 3 with restrictions of pi over 2 is less than B and less than pi.
frenchie is offline  
November 20th, 2007, 08:34 AM   #4
Global Moderator
CRGreathouse's Avatar
Joined: Nov 2006
From: UTC -5

Posts: 16,046
Thanks: 938

Math Focus: Number theory, computational mathematics, combinatorics, FOM, symbolic logic, TCS, algorithms
I'll give you numeric solutions so you can check yourself.




CRGreathouse is offline  
December 7th, 2007, 06:46 AM   #5
Joined: Dec 2007
From: PRC

Posts: 1
Thanks: 0


a) because 0<A<pi/2,sin A=1/squareroot 3
pi/2<B<pi, cosB=-1/2sqrt 3
sinB=sqrt(1-(cosB)^2)=11/(2*sqrt 3)
cos(A+B)=cosAcosB-sinAsinB=-(sqrt 2+sqrt 11)/6

b) sin(A+B)=sinAcosB+cosAsinB=(sqrt(22)-1)/6

c) cos2A=1-2(sinA)^2=1/3

d) cos(A-B)=cosAcosB+sinAsinB=(sqrt 11-sqrt2)/6
lsq6551 is offline  

  My Math Forum > High School Math Forum > Algebra

challenge, problems

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
Any challenge masterofmath Math Events 0 July 3rd, 2013 12:13 AM
challenge NOJEA Computer Science 1 November 3rd, 2012 11:06 AM
Challenge problems kaushiks.nitt Advanced Statistics 3 August 7th, 2009 06:02 PM
Challenge! Help? ida186 Algebra 1 September 11th, 2008 08:58 AM
Challenge 2 agnosticbottle Algebra 11 November 15th, 2007 10:53 AM

Copyright © 2019 My Math Forum. All rights reserved.