# Core 4 Finding minimum value of trig equationWatch

Thread starter 2 years ago
#1
I know how to get max value but not min value q b i and ii
R = SQUARE ROOT 10
a is 1.25
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2 years ago
#2
(Original post by koolgurl14)
I know how to get max value but not min value q b i and ii
R = SQUARE ROOT 10
a is 1.25
The minimum value of is , so the minimum value of and this occurs precisely when or some other reasonable value.
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2 years ago
#3
Easiest way to do this is to say what value of sin(.....) makes sqrt10 sin(.....) as small as possible. Given as you know that sin(...) ranges from -1 to 1, the smallest value occurs when sin(......) is -1, so the minimum value is -sqrt10. As for the second part, you know that sin(x-1.25)=-1, so just solve for x.
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Thread starter 2 years ago
#4
(Original post by Zacken)
The minimum value of is , so the minimum value of and this occurs precisely when or some other reasonable value.
Hmm what about R>0 or does that not affect the results
its the right answer btw im just asking why we should ignore the R>0
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2 years ago
#5
(Original post by koolgurl14)
Hmm what about R>0 or does that not affect the results
its the right answer btw im just asking why we should ignore the R>0
What do you mean by ignoring ?

We have an expression . To minimise this, we look at the variable terms and notice that is bounded between -1 (minimum) and 1 (maximum), so to maximise our entire function we pick the minimum sine value and hence say that the minimum of .
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2 years ago
#6
(Original post by koolgurl14)
Hmm what about R>0 or does that not affect the results
its the right answer btw im just asking why we should ignore the R>0
R>0 only applies to finding the value of R
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Thread starter 2 years ago
#7
Ahhh I see what you mean its just cause in the question it says the range of R is R>0 so I got confused but I guess its not actual R being less than 0?
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2 years ago
#8
(Original post by koolgurl14)
Ahhh I see what you mean its just cause in the question it says the range of R is R>0 so I got confused but I guess its not actual R being less than 0?
Ohh, it just means that when you do then you have but since you pick since
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Thread starter 2 years ago
#9
(Original post by Zacken)
Ohh, it just means that when you do then you have but since you pick since

ohhhhhh that makes a lot of sense thanks alot
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2 years ago
#10
(Original post by koolgurl14)
ohhhhhh that makes a lot of sense thanks alot
No problem!
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