My Math Forum Maximum/Minimum value of trigonometry function

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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/[11-5cos(x/2-45)] and 8/[3-sin x] at the least positive value of x at which it occurs. I understand doing 11-5cos(x/2-45) as being -1*(-5)+11>11-5cos(x/2-45)>1*(-5)+11 16>11-5cos(x/2-45)>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: 7,783 Thanks: 1025 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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### how to find max value of trigonometric functions in denominator and numerator

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