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Trig functions, finding co-ordinates

  • #1

Homework Statement



I have a graph with the functions f(x)=sin2x and g(x)=cosx. The 2 graphs intersect at point B. They want me to find the co-ordinates of B.

Homework Equations





The Attempt at a Solution



Must I equate the two graphs?

sin2x = cosx
2x = 90-x, 3x = 90, x=30 or 2x = 180-(90-x), x=90

It doesnt seem right, is their any other steps?
 

Answers and Replies

  • #2
3,812
92
Aren't you given any specific range within which you want the solution, both the graphs intersect at many points.
 
  • #3
they say that f and g intersect at A(30:0.87) and B.
the domain is xE[0;270].
Thats all that is given.
 
  • #4
jbunniii
Science Advisor
Homework Helper
Insights Author
Gold Member
3,394
180
Do you know a trig identity for sin(2x)?
 

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