Grammar - past tense.

In lesson 8.3 Roberto uses the phrase Io credo di aver perso. Why is this form used instead of ... ho perso?

Hi AnthonyM25, 

Thanks for your question, very interesting point :) 
The verb "credere" (to believe) is a verbo servile (modal verb) and needs to be accompanied by the preposition "di" + infinitive form ("aver" is an abbreviation of "avere").
Hence, Roberto says "credo di aver".

Hope this helps :) 

Many thanks for your reply. 

I have another question about the past tense. In lesson 5.7 (Dinner Phrases, Delays, Expressing Choice), "Piacere" is covered in some detail. In the section entitled "Present  Perfect Tense" conjugates like these appear:

Mi è piaciuto
Ti è piaciuto
Ci è piaciuto
Vi è piaciuto
Gli è piaciuto

Notice that the form of essere is always "è".  This really confuses me because I thought it should be conjugated for each case, i.e.,
 
Mi sono piaciuto
Ti sei piaciuto
Ci siamo piaciuto
Vi siete piaciuto
Gli sono piaciuto

So I tried to look it up and kept getting confused -- in part because it was hard to find conjugations of the "Present Perfect" -- but I found a lot of "Passato Prossimo".  For example, on this website:
https://www.italian-verbs.com/italian-verbs/conjugation.php?parola=piacere

So is the Present Perfect different from the Passato Prossimo? If so, why is it so hard to find conjugations of the "Present Perfect" out there? I must be missing something because throughout the rest of Lesson 5.7, including all the testing, it's all conjugated with "è" for essere as indicated above, and it's hard to imagine such a large portion of the Rocket Italian lesson would be wrong.

Thanks for the help

Hi Tony1248,
 
The verb “piacere” is not extremely straightfoward, especially when comparing it to the English language. It's mainly and most frequently used to express that “someone likes something”.

For instance, let's take the sentence “I like the house”, where “I” is the subject and “house” is the direct object.
This sentence is translated as “Mi piace la casa”. The literal translation reads “To me the house is pleasing": “la casa” becomes the subject, and “to me” the indirect object.

By following this rule, you will then be able to coniugate the verb accordingly, as explained in lesson 5.7. For instance, let’s talk about what “I” like:
-Mi piace (present tense)
-Mi piaceva (imperfect tense)
-Mi è piaciuto (present perfect tense)
-Etc.
 
Although this is the most frequent use of the verb “piacere”, it’s important to note that this verb can also be conjugated like other Italian verbs, for instance:
Present tense:
- io piaccio
- tu piaci
- lui/lei piace
- noi piacciamo
- voi piacete
- essi/esse piacciono
 
In this way, the literal translation would be “to be pleasing”. Hence:
io piaccio = I am pleasing
tu piaci= you are pleasing
lui/lei piace = he/she is pleasing
noi piacciamo = we are pleasing
voi piacete = you are pleasing
essi/esse piacciono = they are pleasing
 
Again, most of the times this verb is accompanied by the indirect object, as in:
tu piaci al mio amico = literal translation: you are pleasing to my friend
 
 
To recap:
the verb “PIACERE” is mainly and most frequently used to express that you like something, as in “I like skiing”. However, it can also be used to express that you are pleasing to someone, as in “I am pleasing to the new teacher”.

I hope this clarifies the use of this verb but please let me know if you have further doubts or questions, I'll be extremely happy to provide further details and examples.
 

Thank you for your response.  I understand best through specific examples. Using the examples I gave in my question:

 If one thing was pleasing in the past: 
Mi è piaciuto
Ti è piaciuto
Ci è piaciuto
Vi è piaciuto
Gli è piaciuto

Or, if multiple things were pleasing: 
Mi sono piaciuto
Ti sono piaciuto
Ci sono piaciuto
Vi sono piaciuto
Gli sono piaciuto

If the above is correct, that explains why the other conjugations of essere (sei, siamo, siete) would never be used with  these kinds of  piacere  expressions.

Thanks for your examples. Indeed, if one thing was pleasing in the past, you would say:
Mi è piaciuto/a (you need to end the verb with "o" or "a" depending on the gender of the object; "Mi è piaciuto il mare" - "Mi è piaciuta la casa")
Ti è piaciuto/a=Something was pleasing to you
Ci è piaciuto/a=Something was pleasing to us
Vi è piaciuto/a=Something was pleasing to you
Gli è piaciuto/a=Something was pleasing to him/them
Le è piaciuto/a=Something was pleasing to her/formal "you"

However, if multiple things were pleasing, you need to say:
Mi sono piaciuti/e (you need to end the verb with "i" or "e" depending on the gender of the objects; "Mi sono piaciuti i pittori" - "Mi sono piaciute le fotografie")
Ti sono piaciuti/e=Multiple things were pleasing to you
Ci sono piaciuti/e=Multiple things were pleasing to us
Vi sono piaciuti/e=Multiple things were pleasing to you
Gli sono piaciuti/e=Multiple things were pleasing to him/them
Le sono piaciuti/e=Multiple things were pleasing to her/formal "you"

Said this, please note that the other conjugations of "essere" can also be used, but they will refer to other subjects. For instance, if you state "Mi sei piaciuto" it means that "you" were pleasing to me; if you state "Le siamo piaciuti" it means that "we" were pleasing to her; if you state "Ti sono piaciuti" it means that "they" were pleasing to you and so on.

To recap: the "complemento di termine" (mi, ti, le, gli, ci, vi) indicates the person to whom the thing is pleasing. The verb "essere" needs to be conjugated to the subject of the verb "piacere", the thing that is pleasing. 

Let me know if you have further questions!