In △ ABC, cos (a + b) = - (12 / 13), cosa = 4 / 5, Tan β is obtained

In △ ABC, cos (a + b) = - (12 / 13), cosa = 4 / 5, Tan β is obtained

From the title: sin (a + b) = 5 / 13, Sina = 3 / 5. Cos (a + b) = cosacosb - sinasinb = 12 / 13; sin (a + b) = sinacosb + sinbcosa = 5 / 13; substitute Sina = 3 / 5, cosa = 4 / 5 into the above two equations to get SINB, CoSb and tanb
LZ, can I give you some ideas?
Tan (a + b) can be obtained by cos (a + b)
Tana can be obtained from cosa
Then expand Tan (a + b) and substitute it into Tana
Finally, we get Tan β
I don't understand~~
A proof of trigonometric function
Tan (π / 4 + a) = (COSA + CoSb) (COSA Sina). In the process of solution, we can't move the formula on the right side of the equal sign. We can get the formula on the left side directly
Wrong number, it should be tan (π / 4 + a) = (COSA + Sina) / (COSA Sina)
tan(π/4+A)=sin((π/4+A)/(cosπ/4+A)=
(sinπ/4cosA+cosπ/4sinA)/(cosπ/4cosA-sinπ/4sinA)=
(√2/2cosA+√2/2sinA)/(√2/2cosA-√2/2sinA)=
(cosA+sinA)/(cosA-sinA)
The difference between of plus noun and adjective
What's the difference between them? Which nouns are suitable to use of plus nouns?
Of + noun = adjective
For example: environment protection is of great importance
Environment protection is important
Another form of possessive case of noun is formed by preposition of and noun. It is mostly used to express inanimate things (including plants)
What is the name of this street?
But pay attention to the differences
1. Possessive's = = > someone, thing, thing has a subject in front of it
e. My pen, my mother's car, God's love
2. A is contained in B = = > with the preposition of
e. The power of love, one of my friends
Tom is [] (funny) in my class
the funniest
Tom is funnier in my class.
Tom is the funniest in my class.
funnier
Be alth (adjective) Tom (noun possessive)
healthy
Tom's
The comparative and superlative usage of adjectives and adverbs
It needs to be explained in detail
1、 Master the formation of comparative grade of adjectives and adverbs and the irregular changes of good, well, many, much, etc. master the comparison of two and three or more people or things by using the sentence patterns learned. Master the usage of modifying comparative grade by using adverbs such as many, a little, etc
The usage of verbs, adjectives, adverbs, prepositions and conjunctions
Verbs, adjectives, adverbs, prepositions, conjunctions, who can tell me the usages of these words, before and after, when to use them, what words to match with, etc. The more detailed the better. If the answer is not good, I am willing to add more points
Verb as predicate, adjective as predicative or modify noun and pronoun, adverb modify verb adjective or adverb, preposition followed by object and often appear in fixed collocation, conjunction connects two same components
Faint
What are the characteristics and usages of adverbs, prepositions, adjectives, nouns and verbs in English?
Can list sentence description, and point out the part of speech contained in the sentence! Fast, easy to understand!
Adverbs are used to modify adjectives and verbs. Take very for example, she is very beautiful, very modify beautiful, which means a degree. Thank you very much
Prepositions are used for linking, such as in On, on, on Note that some words are sometimes adverbs, such as "on" in "come on", which has no practical meaning
Adjectives are used to describe a person and a thing. It's very simple. For example, she is beautiful. Beautiful is an adjective
Verb is more simple, which means action words, come, go, go, give
All languages are interlinked. Learning Chinese well will also help you learn English well. Come on!
What's the difference between the superlatives of adjectives and adverbs?
Many more itself is not a whole. For example, "many more people" is the meaning of many other people and more people, In fact, it is a usage: more can be placed after the numeral or any, some, no, a few, a little, many, many, to indicate additional, additional, and more. The meaning of "much more" is rich, and it is followed by an uncountable noun. In addition to the same usage as "many more", it can also be used as a comparative degree. At this time, more is a simple adjective of comparative degree, Meanwhile, more can not only be used as a comparative degree alone, but also form a comparative degree together with the morpheme. At this time, the word "more" is used to modify the whole comparative degree instead of just modifying "much" But don't think it too complicated, it and more directly for the comparative grammar is the same, but the comparative level after the multi is a little longer. Finally finished. But I advise you to find less such grammar problems in the future, easy to make people dizzy, after doing the questions, think more and sum up can do. At the beginning may have a little maladjustment, a long time is good! I wish you success as soon as possible!
First of all, adverbs can modify adjectives, but some can only modify the original form of adjectives (very so too), some can only modify the comparative level (much even a bit a / little)
As an adverb of degree, much modifies more Its usage is the same as more. It is often followed by polysyllabic adverbs and adjectives. Because it has many modifier nouns, it is only followed by uncountable ones. There is no difference in the composition of the superlatives of adverbs and adjectives. According to their stanzas, they are divided into monosyllabic, disyllabic and polysyllabic words, and the corresponding changes are regular. Please refer to the grammar book again.
What is the part of speech combination of Adverb + of and Adjective + of? Is it a compound preposition phrase and an adjective phrase
The adjective + of is equivalent to a nominalized phrase, such as typical of
Adverb + of, such as out of
By the way, is full of an adverb or an adjective?
Adverb + of and Adjective + of are the combination of part of speech. They are compound prepositional phrases and adjective parts of speech. Adverbial is a joint element in front of a noun, which is used to modify, limit, verb or adjective, indicating the state, manner, time, place or degree of action