



 
Alex, I would start by reminding myself of the definition of lag base 2.
The xintercept is the point on the curve where y = 0. From (1) is 0 = log_{2}(log_{2}x) then log_{2}(x) = 1 and then from (1) again x = 2. Thus the xintercept is (2,0). To find the slope of the tangent to the curve at this point you need to find the derivative of y = log_{2}(log_{2}x) with respect to x. This in going to involve the chain rule and the derivative of log_{2}x. Again using (1),
Differentiate both sides with respect to t to obtain
and hence
Use this fact and the chain rule to differentiate y = log_{2}(log_{2}x) and then evaluate the derivative at (2, 0). Harley  


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