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Mathematics Question Thread
jakesilove:
--- Quote from: aqsarana_ on February 20, 2016, 03:51:20 pm ---Hi!
At the moment I'm doing HSC Trigonometry and I'm really confused about when to change the calculator's mode to Degrees or Radians. How can i be able to tell when to change the mode?
Thank You.
--- End quote ---
Definitely agree with all of the above: If the question mentions degrees, use degrees. If the question doesn't mention degrees, use Radians. Simple as that! If you sometimes get confused, maybe it is worth getting into the habit of highlighting every time you see a degrees symbol in a question, so you know you need to put your calculator into degrees mode.
Jake
Phillorsm:
Hey jake, having trouble integrating this.
Integrate (4-(x-8)^2)^(1/2)
I know its a semicircle and the limits are 10 to 6, but I keep getting zero.
Is there a special way to integrate a semicircle and find the area? (Other than (pi*r^2)/2 )
Happy Physics Land:
--- Quote from: Phillorsm on February 21, 2016, 09:57:47 pm ---Hey jake, having trouble integrating this.
Integrate (4-(x-8)^2)^(1/2)
I know its a semicircle and the limits are 10 to 6, but I keep getting zero.
Is there a special way to integrate a semicircle and find the area? (Other than (pi*r^2)/2 )
--- End quote ---
Hey Phillorsm:
Is your question a definite or indefinite integral?
Assuming that your question is an indefinite integral, the answer should not be zero because after all, area cannot be zero right? I like your approach of drawing a semi-circle and you have correctly identified the domain of the semi-circle. So all you really had to do was apply pi(r^2)/2 to find the area of the semi circle, and that will give you the integral (l believe you have identified that r=2 because 4 = 2^2). Considering that this is an indefinite integral question, you will need to add +C at the end.
(sorry just ignore the sintheta stuff in the background, they are irrelevant)
If you have any further questions dont hesitate to ask!
Best Regards
Happy Physics Land
jakesilove:
--- Quote from: Phillorsm on February 21, 2016, 09:57:47 pm ---Hey jake, having trouble integrating this.
Integrate (4-(x-8)^2)^(1/2)
I know its a semicircle and the limits are 10 to 6, but I keep getting zero.
Is there a special way to integrate a semicircle and find the area? (Other than (pi*r^2)/2 )
--- End quote ---
Hey Phillorsm!
If you are looking to find the area underneath that curve, you've identified one great way to do it: by understanding that the graph is a semicircle, use the formula (pi*r^2)/2 !
However, you should also be able to integrate as normal and find the required result. I'm not at home at the moment, so can't write out a full solution, but hopefully someone else on the forums can!
Hope this helps! Let me know if there's anything you're unsure of.
Jake
Loki98:
Could someone please help with question 10a of the 2003 2u mathematics hsc paper :)
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