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# differentiation watch

1. Can someone please help me with this question below. From differentiation
The question is At time t minutes after being switched on, the temperature of an oven is theta
given by theta=190-175 e^ -0.08t

the answer to the first part was 'find the time taken to reach a temp of 160 was 22min I got that, but I dont think thats relevant for the next part

find the rate at which the temperature is increasing when theta is 50
so I plugged in theta and differentiated to find t and got something weird
I them tried differentiating and then plugging in the value-but that didn't work.

the answer is 11.2 degrees, unless its wrong :P
2. Differentiate before you substitute the value.

3. I have checked and the answer is correct.

You need to find the value of t when theta = 50 and this is probably where you are going wrong.
4. (Original post by Mr M)
I have checked and the answer is correct.

You need to find the value of t when theta = 50 and this is probably where you are going wrong.

ohhhhh :P thank you! that'll explain hah!
5. (Original post by Mr M)
I have checked and the answer is correct.

You need to find the value of t when theta = 50 and this is probably where you are going wrong.

yep 11.2 thanks!
6. (Original post by AishaTara)
yep 11.2 thanks!
Good.

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