In △ ABC, if a = 5, B = 3, C = 120 °, then Sina=______ .

In △ ABC, if a = 5, B = 3, C = 120 °, then Sina=______ .

∵ C2 = A2 + b2-2abcosc = 52 + 32-2 × 5 × 3 × cos120 ° = 49, ∵ C = 7. So from Asina = csinc, Sina = asincc = 5314
In △ ABC, a = 5, B = 3, C = 120 ° to find Sina
c^2=a^2+b^2-2abcosC=25+9-2*5*3*(-1/2)=49
C=7
a/sinA=c/sinC
5/sinA=7/(√3/2)
sinA=(5/14)√3
In the triangle ABC, a = 4, B = 6, C = 120 °, what is Sina
Are you from junior high school or senior high school? Junior high school: extend AC to D. make CD perpendicular to ad, angle ACB = 120 degrees, angle DCB = 60 degrees, angle d = 90 degrees, then angle DBC = 30 degrees, because BC = 4, so CD = 2, BD = 2 √ 3 in right triangle ADB, ad = AC + CD = 6 + 2 = 8, BD = 2 √ 3, so hypotenuse AB = 2 √ 19, so Sina = BD / AB = 2 √ 3 / 2 √
To solve the linear equations of three variables: x-4y + 3Z = 1; 2x + 5y-3z = - 2; 3x + y-2z = 1
Equation (1) * 2, then use equation (2) - equation (1) = 13y-9z = - 4, then use equation (1) * 3, then use equation (3) - equation (1) = 13y-11z = - 2 to get z = - 1, and then substitute into the formula of (2) - (1) to get y = - 1, x = 0
x=0 y=-1 z=-1
x=0,y=-1,z=-1
In the range of natural number, the solution of equation 3x + y = 10 is______ .
The solution of the equation 3x + y = 10 is obtained from the meaning of the problem, and if x and y are all natural numbers, then y = 10-3x, ∵ x, y are all natural numbers, ∵ y = 10-3x ≥ 0 {x ≤ 103; and ∵ x ≥ 0 and X is a natural number, ∵ x can only be x = 0, 1, 2, 3
Simple operation of (2x-y) (3x-4y) - 2 (X-Y) (2x-5y)
The original formula = (6x & # 178; - 8xy-3xy + 4Y & # 178;) - 2 (2x & # 178; - 5xy-2xy + 5Y & # 178;)
=6x²-11xy+4y²-4x²+14xy-10y²
=2x²+3xy-6y²
Find the natural number solution of the equation 3x + 4Y = 12. There is a question, that is, what does the natural number solution mean? Help me, tell me
First of all, you need to understand what natural numbers are. Natural numbers are 0 1 2 3 An integer greater than or equal to zero
Natural number solution means that the solution should be found in natural number, so x = 0, y = 3, x = 4, y = 0
Natural number refers to:
How to write the steps?
The known monomial formula 5x ^ B + 5Y ^ 3a is the same as the monomial formula - 4x ^ 2ay ^ 2-4b. To find the value of a and B, the known monomial formula 3x ^ 5ay ^ B + 4 is the same as the monomial formula - 5x ^ 1-2by ^ 2
(1) a=2/11 b=4/11
(2)a=1/5 b=0
If the solution of the equation 4x + 5 = 3x + 6 about X is the same as that of 2x-a = 0, the value of a is obtained
4x+5=3x+6
The solution is x = 1
Substituting into the second equation: 2-A = 0
A = 2
In the first equation, x = 1 can be obtained directly, and a = 2 can be obtained by substituting a directly
First find the solution of 4x + 5 = 3x + 6
4x-3x=6-5
X=1
Substituting 2x-a = 0
We can get a = 2x = 2 * 1 = 2
A=2
（4x+5=3x+6→x=1
2x-a=0→2*1-a=0→a=2）