SOLUTION: Determine the number of roots of the equation. cosx� = 10/x which lie in the interval -180 <x < 180. In the textbook it says "by drawing suitable sketch graphs." That might be

Question 942196: Determine the number of roots of the equation. cosx� = 10/x which lie in the interval -180 In the textbook it says "by drawing suitable sketch graphs."
That might be difficult to show here but could someone please explain how to go about doing this? I know roots are where y=0 and by the usual cos x wave then there are two roots at 90 and -90. I thought about substituting x=10 into the equation and then I got 10/10 which equals 1 and then x=arccos1=0 so I was wondering if that is then a root. Although I'm not entirely sure. Any help at all would be appreciated.

Answer by richard1234(7193) (Show Source): You can put this solution on YOUR website!
"I know roots are where y=0"

What is y? And not quite, in this case.

First, sketch

. Then sketch

. The roots are the x-coordinates of the intersection points.
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