Help with a few high school math problems, help watch a few high school math problems.

1.In ABC, if sina:sinb:sinc=m:n:l, and a+b+c=s, then a=

2.In ABC, (a*a+b*b)sin(a-b)=(a*a-b*b)sin(a+b), the shape of the abc is judged.

3.It is known that the side lengths of the circumscribed quadrilateral ABCD are AB=2, BC=6, and CD=DA=4 respectively, and the area of the quadrilateral ABCD is found.

In fact, love is short-lived, and sometimes I think it's the same as soliciting. As soon as the little hand is pulled, as soon as it is loosened, a woman will pass, ao The little hand is pulled, not loosened, a woman will be in hand, ao What is the most painful thing in love, do you know? It's so easy to talk about, it's someone else's woman.

What is the most painful thing about being in love, do you know? It's so easy to talk about, it's a same-sex person.

I really want to help you, but I graduated from high school, all the books are sold, I can't find a notebook, to be honest, the topic is not about how much to do, the main topic should be refined, and I can draw inferences! And the formula for the trigonometry part is really important, (doubling angle, and differential product...).Including the universal formula) If you want to revisit these in college, you should memorize them now and be able to use them flexibly!

Let him write the names of all trigonometric functions, give the half-angle formula for sin, cos, and ask him to write the multiplier formula for all trigonometric functions.

I'm too old to do it, so I'll give you two proof questions, it's very simple, the first one is to simplify the formula of tan into sin than cos.

Second, the denominator is rationalized, that is, the numerator and denominator are the same as sina-icosa simplification.

First, some common basic knowledge and basic principles of trigonometric functions must be mastered, such as sin, cos, tan, and cot, and the distribution relationship of each quadrant must be understood.

Second, the basic principles and operations of complex numbers should be carefully understood, and the questions are generally very simple and purely for giving points.

Third, the operation of trigonometric functions is the hot, important and difficult point of the exam. In the initial study, it is necessary to lay a good foundation to prepare for future exams, and at the same time, it is necessary to practice more similar question types.

Good luck with your learning and progress.

I, 1, A2, B

3、b4、a

5, c6, no.

7. I can't see the answer clearly, anyway, is it i, is it b? See for yourself.

8, b two, 1,

iii 28i, 10, 6, 8

IV. sin67°30 cos67°30

sin2×67°30′

sin135°

sin45°

2、a/sina=b/sinb

a=6/(√3/2)

a=4 3 don't want to play ......

It's all pretty simple, let him do it himself.

I, 1, D2, B

3、b4、a

5、c6、b

7, C8, B two, 1,

iii 28i, 10, 6, 8

IV. sin67°30 cos67°30

sin2×67°30′

sin135°

sin45°

2、a/sina=b/sinb

a=6/(√3/2)

a=4√33、（1-i)^3=（1-i)*(2i)=-2i-24、t=-x-1=1/4(2-y)

y=4x+6

3,6) to the straight-line distance |-6+12+6|Root number 17 = 12 root number 17 five, 1, tan( +=sin( + cos( +=(sin cos +sin cos) (cos cos -sin sin ) = (cos tan cos +cos tan cos ) (cos cos -cos tan cos tan) = (tan +tan ) (1-tan tan )

tan(α-=tan[α+=[tanα+tan(-β/[1-tanαtan(-β=(tanα-tanβ)/(1+tanαtanβ)

cosθ+isinθ）=[(cosθ)^2-(isinθ)^2]/(cosθ+isinθ）=cosθ-isinθ

I really want to say that you are really as good as your name zhangqiangsabi

Really, this is the average high school question, and he can do it.

Looking at the basics in the textbook, it's actually quite simple.

Is it all going to be done?

2.Equivalent to (x-1) (x-4) < 0.

Included in the second question of c, do not discuss the numerator and denominator separately, in fact, the division is equivalent to the multiplication of (x-1)(x-4)<0 when there is no equal sign, then.

m-n pass (x 2-4x-1) x <0, threading the needle lead method, the solution is 2-root number 52 + root number 5

c contains a

1。Focus f(0,3) alignment y=1, p its distance from the x-axis d = distance to the alignment m+1, only the minimum value of m+pq is required. , by the definition m=pf, that is, to find pf + pq is the smallest, when moving to the line between qf is the shortest, and then prove by itself.

2. The minimum value of pm is the distance from m to (0,3) minus the radius, and only the minimum value of the distance from m to (0,3) is required. Establish.

m(x,y),the square of the distance from m to (0,3) = x + (y-3) 1), and m is suitable for hyperbola x 3-y = 1, and x = 3 + 3y is substituted into (1) formula, and the distance from m to (0,3) = 4y -6y + 12 formula can be used.