1. Cos2a / sin (a - π / 4) = - √ 2 / 2, then the value of sina + cosa is? 2. In the triangle ABC, Tana = 1 / 2, CoSb = 3 √ 10 / 10, then the value of Tanc is? 3. To make Sina - √ 3cosa9 = (4m-6) / (4-m) meaningful, then the value range of M is?

1. Cos2a / sin (a - π / 4) = - √ 2 / 2, then the value of sina + cosa is? 2. In the triangle ABC, Tana = 1 / 2, CoSb = 3 √ 10 / 10, then the value of Tanc is? 3. To make Sina - √ 3cosa9 = (4m-6) / (4-m) meaningful, then the value range of M is?

1. Cos2a / sin (a - π / 4) = - √ 2 / 2, then the value of sina + cosa is?
cos2a=(-√2/2)(sinacosπ/4-cosasinπ/4)=(-sina-cosa)/2
cos2a=cos^2a-sin^2a=(-sina-cosa)/2
cos^2a-cosa/2=sin^2a-sina/2
(cosa-1/4)^2=(sina-1/4)^2
So cosa = Sina = √ 2 / 2, cosa + Sina = √ 2 or cosa-1 / 4 = 1 / 4-sina, cosa + Sina = 1 / 2
2. In the triangle ABC, Tana = 1 / 2, CoSb = 3 √ 10 / 10, then the value of Tanc is?
tanA=1/2,2sinA=cosA,4sin^2A=cos^2A,sinA=√5/5,cosA=2√5/5
cosB=3√10/10,sinB=√10/10
sinC=sin(B+A)=sinBcosA+sinAcosB=√2/2
cosC=-cos(B+A)=-(cosBcosA-sinBsinA)=-√2/2
tanC=-1
3. In order to make Sina - √ 3cosa9 = (4m-6) / (4-m) meaningful, what is the value range of M?
sina-√3cosa9?sina-√3cosa?
-2
Which variables add es and which ones add s?
Don't copy a lot
Let's also talk about the differences and relations among not, is not and it is not,
What is the plural of stomach
stomachs
Ch here pronounces K, plus s
stomaches
S
sure
Es
Add s directly, because ch sends / K /
Is the plural of photo plus s or es
The plural form of photo is plus s, because the words ending with o are living + es and inanimate + S. photo means photo, belonging to inanimate, so + s
Why is there any difference between the plural of photo as photos and the plural of potato as potatoes, one with s and the other with es?
After the nouns ending in O, s, x, CH, SH, add "es". Hero - Heroes box - boxes class - classes Bush - bushes Watch - watches 5. Golden point; A. some loan words or abbreviations ending in o only add "s" B
One of these two words is a loan word, that is, there was no such word in English, which was introduced
Photo is a loanword, only adding s, for example: kilo / Piano and "s"
The second floor is not right. The addition of S is not based on whether there is life or not, but on "most nouns ending with consonant + O are added with ES, with the exception of loanwords such as photo, piano and kilo
There is life, such as heroes, tomatos
Inanimate plus s, such as zoos, photos
This kind of thing is conventional. Language / grammar is regular, but there are many special cases that need to be memorized one by one. This is the real difficulty in learning
There are four words that must be added with ES, Negro, hero, potato and tomato
For the rest, just add s, and for a small part, add s and es.
Photo is an exception. Remember it
Is the plural of photo plus es?
Remember: Black heroes eat tomatoes and potatoes
These four words Negro, hero, tomato and potato are added with - es
Add - s to the rest ending in o
photos
Plus s
Add es
You just need to remember the following words:
potato + es
tomato + es
hero + es
Negro + es
Middle school teachers call these four words "two people, two dishes".
When you come across other words like this, add s.
Add s directly -- photos
Is the plural "photo" followed by "es" or "s"
Plus s is right
The one on the first floor is wrong
Teach you a way
If the word "O" means something that can be eaten, add es, because you can add more seasoning to the food
If you can't eat... Add less... Just add s
This is special
Ha ha... Isn't it funny?
Photo plural plus s / es?
Add s
Generally, living matter is added with ES, on the contrary, inanimate matter is added with S. photo is inanimate, so s is added
What is the plural of building? For example, "two building" should be in English?
Building (singular) buildings (plural)
Two buildings (two building)
two buildings
+s
The countable noun is buildings
Uncountable is construction project
Two are two buildings
The complex number of building is buildings, + s
Two buildings
+S
A building
2 buildings
Don't add s after the plural of nouns
1.1 construction method and pronunciation rules 1) in general, add – s: map maps boy boys girl girls pen pens bag bags car cars after clear consonants / S / voiced consonants and vowels / Z / 2) add – es, read / iz / bus buses watch watches box-B at the end of S, SH, Ch, X