Find dy/dx if. y = inverse of cos x

And explain how you got it so i can understand future problems : 3

Which themes are portrayed in this excerpt from leo tolstoy’s the death of ivan ilyich? praskovya fedorovna came of a good family, was not bad looking, and had some little property. ivan ilyich might have aspired to a more brilliant match, but even this was good. he had his salary, and she, he hoped, would have an equal income. she was well connected, and was a sweet, pretty, and thoroughly correct young woman. to say that ivan ilyich married because he fell in love with praskovya fedorovna and found that she sympathized with his views of life would be as incorrect as to say that he married because his social circle approved of the match. he was swayed by both these considerations: the marriage gave him personal satisfaction, and at the same time it was considered the right thing by the most highly placed of his associates. so ivan ilyich got married. conforming to social conventions criticism of a middle class lifestyle the destructive impact of loneliness struggling to face reality the necessity of companionship

Liz had 140 pens and inna had 100 pens. after inna gave liz some pens, liz had 3 times as many pens as inna. how many pens did inna give liz?