Login

If 3sinA = 2cos2A. find A

3sinA=2cos^2A 
now cos^2A=1-sin^2A from identity
3sinA=2(1-sin^2A)
​3sinA=2-2sin^2A
2sin^2A+3sinA-2=0
on solving the quadratic equation we get
(sinA+2)(2sinA-1)
sinA cannot be -2 
therefore sinA=1/2
sin30=1/2
therefore A is 30
hope this helps!!!

  • 4
View Full Answer
3sinA=2cos^2A . Find A . Proof = 3sinA=2(1-sin^2A) so 3sinA=2-2sin^2A or 2sin^2A+4sinA-sinA-2=0 . Then 2sin(sinA+2)-1(sinA+2).Then sin = 1/2 or sin = 2 . So if sin =1/2 then the value of A is 30 degree.
  • 1
3sinA=2cos^2A 
now cos^2A=1-sin^2A from identity
3sinA=2(1-sin^2A)
​3sinA=2-2sin^2A
2sin^2A+3sinA-2=0
on solving the quadratic equation we get
(sinA+2)(2sinA-1)
sinA cannot be -2 
therefore sinA=1/2
sin30=1/2
therefore A is 30
hope this helps!!!
  • 3
What are you looking for?