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May 31st, 2015, 10:01 AM  #1 
Newbie Joined: May 2015 From: Singapore Posts: 2 Thanks: 0  Maximum/Minimum value of trigonometry function
Hi, This is a common CIE A levels P1 paper question, but I seem to have forgotten how to do it: Find the maximum value and the minimum value of 30/[115cos(x/245)] and 8/[3sin x] at the least positive value of x at which it occurs. I understand doing 115cos(x/245) as being 1*(5)+11>115cos(x/245)>1*(5)+11 16>115cos(x/245)>6 and so on... but how do I do this if there is a fraction? Any help would be appreciated, thank you in advance! 
May 31st, 2015, 10:19 AM  #2 
Global Moderator Joined: Oct 2008 From: London, Ontario, Canada  The Forest City Posts: 7,574 Thanks: 931 Math Focus: Elementary mathematics and beyond 
As both denominators are always positive you don't have to consider negative values. With the denominator and numerator positive, a fraction with a constant numerator is at a maximum where the denominator is smallest and at a minimum where the denominator is largest. 
May 31st, 2015, 11:40 AM  #3 
Newbie Joined: May 2015 From: Singapore Posts: 2 Thanks: 0 
Hmm... sorry, I still don't understand that. How would you solve the above 2 questions though? Thank you 

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