Answer:
a) 10.10 a.m. , (b) 10.20 a.m. which is 10 minutes after sprints start , (c) The students work at 10.50 a.m. , (d) For 60 minutes from 10 a.m. to 11 a.m. which equals to 1 hour
7 is incorrect. The answer should be -4. Here's how I'd derive it:

With
, we should expect
. If
, then

Also,

so we should expect
and

You seem to be taking

but this is not an identity.
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8 is incorrect. Just a silly mistake, you swapped the order of the terms in the numerator. It should be

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9. Use the identity from (7).
lies in the second quadrant, so

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12.




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13.




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14.



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15.



I think A is 2 and B is 3 and C 2
3(8)-12=12
24-12=12
The fourth choice.
Yeah I think you already got it
Answer will depend on the value of the radius. If radius is 6 and height is 7, volume is: 791.28 m^3
If radius is 7 and height is 6, volume is: 923.16 m^3