Question

@Michele_Laino

Answer 1

I got C

Answer 2

I give you the identity to solve this question:
\[\sum_{i=1}^{n}i ^{2}=\frac{ n(n+1)(2n+1) }{ 6 }\]
and:
\[\sum_{i=1}^{n}i=\frac{ n(n+1) }{ 2 }\]
both those formulas can be demonstrated usin the induction principle on n

Answer 3

please try this substitution:
\[\cos x=t\]
and use this identity:
\[\sec x=\frac{ 1 }{ \cos x }\]

Answer 4

so it is C

Answer 5

no sorry!

Answer 6

i meant d!!

Answer 7

furthermore, plea\[\tan x=\frac{ \sin x }{ \cos x }\]se use this identity:

Answer 8

why D?

Answer 9

can you show your work, please?

Answer 10

oh then it is B

Answer 11

im in a rush please

Answer 12

I don't know if it is B

Answer 13

\[=\int\limits \frac{ \sin x }{ (\cos x)^{2} }dx=-\int\limits \frac{ dt }{ t ^{2} }=\frac{ 1 }{ t }=\frac{ 1 }{ \cos x }+C\]
after the substitution t=cos x

Answer 14

@mondona I understand you, nevertheless please note that I can not give you your answer directly, since the code of conduct

Answer 15

bye! :) @mondona