Help me suggest a book

[Jacob]

Hi, I'm doing currently doing Cal 1 and my foundation in Trigonometric are not good. I can solve Limits, Differentiation, and Integral when the problems are numbers but when it has Trigonometric in it some times I couldn't solve it.

I was solving a problem that requires me to use the L'hopitals rule and I got to a point where I need to use the Product rule to solve it. Stucked at this point.
cos(x)cos(x) + 2 [sin(x)-sin(x)] / 10x

I understood that sin(x) - sin(x) become 0 but wondering how cos(x)cos(x) become 1? This just one of the problems I encountered today. I'm really want to master problems that involve trigonometrics. Any recommendations of books or YT videos that could improve my foundation? Thank you

 

[Dr.Peterson]

Hi, I'm doing currently doing Cal 1 and my foundation in Trigonometric are not good. I can solve Limits, Differentiation, and Integral when the problems are numbers but when it has Trigonometric in it some times I couldn't solve it.

I was solving a problem that requires me to use the L'hopitals rule and I got to a point where I need to use the Product rule to solve it. Stucked at this point.
cos(x)cos(x) + 2 [sin(x)-sin(x)] / 10x

I understood that sin(x) - sin(x) become 0 but wondering how cos(x)cos(x) become 1? This just one of the problems I encountered today. I'm really want to master problems that involve trigonometrics. Any recommendations of books or YT videos that could improve my foundation? Thank you

Please show the actual problem!

My guess is that this is a limit at 0, and cos(0) = 1, so that may be the answer. But we can't be sure without that information!

And your title caused me not to read this until now, because I assumed you were just asking for a book recommendation. There are some good free textbooks available online; you'll probably want a precalculus book such as this one: https://math.libretexts.org/Bookshe...tigation_of_Functions_(Lippman_and_Rasmussen) or this one: https://openstax.org/details/books/precalculus