Mathematics Compulsory 5, Sine Theorem. Detailed process. Thank you! 30

In fact, these questions can be decided, and it is enough to draw only one kind of picture.

First of all, draw an angle, which is called angle a, whether it is an acute angle or an obtuse angle according to the title. Then cut out the length of the b side on one of the edges of the angle, and you try to make the A side corresponding to the angle a, and there are several solutions that can be made.

For example, when the first question asks a b, with the other endpoint of the b side as the center of the circle and the length a as the radius (note that the length does not exceed b), there can only be one intersection point with the third side, that is, there is a solution. The same is true for other questions, which involve BSINA, and it is enough to cross the other end of the B side to make a perpendicular line on the other side.

It is best to use this method to determine the number of triangle solutions, and this method is very useful.

Be smart, these are all, and you don't even have a chance to use them during exams. I said it might as well be guessed... Get the vertical relationship right.

Do more questions, understand slowly, it is not possible to rely on speaking, math is the last word, you can try to use the cosine theorem.

This compulsory 5 is very clear above.

Why don't you read a book?

1. (1) Obtained from sinc = 2 sina: sinc sina = ab bc = 2, so ab = 2 times the root number 5 by two-fifths

2) cosa = (ac square + ab square - bc square) (2 * ac * ab), filial piety to two times the root number 5. Skillfully slow the cover, so sina = the root of the fifth of the number 5. So sin(2a-4) = 2 points of the root number of the second * (sin2a-cos2a) = the root number of the tenth of which is earlier 2

1. Sinusoidal key theorem: a sina=c sinc. a=2c =>a/sin(2c)=c/sinc=>cosc=a/2c...1)

cosc=(a^2+b^2-c^2)/2ab...2) Simultaneous (1) (2) has a 2c = (a 2 + b 2-c 2) 2ab....3)

and b=4....4)

a+c=8...5)

Synoptic (3), (4), (5) has a = 24 5 or a = 4 (rounded off because angle a is greater than angle b is greater than angle c).

So digging a = 24 5, c = 16 5

Question 2 Is it equal to three thirds of the root Can you see clearly?!

Convert tana tanb into sin and cos forms, and then divide them.