Is there any way to evaluate
limx→0xcosx−sinxx2
without using L'Hopital's Rule? I was trying to use some of the standard trig limits (e.g. limx→0sinxx=1), etc. but couldn't figure it out.
Thank you.
Answer
Adding and subtracting x in nummerator we can split the expression under limit as cosx−1x+x−sinxx2
The first expression tends to 0 because (1−cosx)/x2→1/2 and the second expression also tends to 0 as shown below.
Since the second expression is an odd function it is sufficient to prove that the expression tends to 0 as x→0+. Next note the famous inequality $$\sin x
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