Given that x is measured in radians and x>20, find the smallest value of x such that
Is this an inequality question?
Can someone please guide me how should I start with
Thanks!!
General solution:
$\displaystyle \cos \left( \frac{x - 1}{3} \right) = - \frac{\sqrt{5}}{4}$
$\displaystyle \Rightarrow \frac{x - 1}{3} = \cos^{-1} \left( - \frac{\sqrt{5}}{4}\right) + 2 n \pi$ or $\displaystyle \frac{x - 1}{3} = \pi + \cos^{-1} \left(\frac{\sqrt{5}}{4}\right) + 2 n \pi$ where n is an integer.
You want the smallest solution for x that is larger than 20.
Of course, if you have access to the appropriate technology you could always use a graph to get the answer .......