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# STEP Question integration by substitution watch

1. (Original post by TeeEm)
just inverse cos in radians
But if this is for step and is radians I don't know how to do it without a calculator,should I learn arccos values etc. smh :?
2. (Original post by Moordland)
But if this is for step and is radians I don't know how to do it without a calculator,should I learn arccos values etc. smh :?
I see what the issue is

most definitely you must learn
3. (Original post by TeeEm)
I see what the issue is

most definitely you must learn
Thank you aha will do
4. (Original post by Moordland)
Thank you aha will do
If you are interested, it is because most of the (trigonometric) calculus is based on the fact that if x is small and in radians, then sin x is approximately equal to x. A proof is here https://www.youtube.com/watch?v=vz9_102nL8M, it is some very elegant and good maths.

With this, we can derive that d/dx (sin x) = cos x, and so on.
5. (Original post by Omghacklol)
If you are interested, it is because most of the (trigonometric) calculus is based on the fact that if x is small and in radians, then sin x is approximately equal to x. A proof is here https://www.youtube.com/watch?v=vz9_102nL8M, it is some very elegant and good maths.

With this, we can derive that d/dx (sin x) = cos x, and so on.

Ah this makes sense!

I remember you, you were one of the good posters haha. Are you taking step 2+3 this year?
6. (Original post by Moordland)
Ah this makes sense!

I remember you, you were one of the good posters haha. Are you taking step 2+3 this year?
Haha I hate knowledge being thrown at you without any sense to it, hence why I was urged to clear it up for you.

I've just done step 1,2,3 and I'll be starting at Cam in October, would be more than happy to try and help you with arising problems (which there were numerous for me)
7. (Original post by Omghacklol)
Haha I hate knowledge being thrown at you without any sense to it, hence why I was urged to clear it up for you.

I've just done step 1,2,3 and I'll be starting at Cam in October, would be more than happy to try and help you with arising problems (which there were numerous for me)
Thank you.

Congratulations.
8. (Original post by Moordland)
Thank you that seems nicer, may I ask why in radians is that by convention.
How long ago did you take your maths and FM A Levels?

Could you post questions in Maths rather than Maths Exams please?
9. (Original post by Mr M)
How long ago did you take your maths and FM A Levels?

Could you post questions in Maths rather than Maths Exams please?
Last year.

And sorry.

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