How do you do this?please help
1 answer:
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I love these. It's often called the Shoelace Formula. It actually works for the area of any 2D polygon.
We can derive it by first imagining our triangle in the first quadrant, one vertex at the origin, one at (a,b), one at (c,d), with (0,0),(a,b),(c,d) in counterclockwise order.
Our triangle is inscribed in the rectangle. There are three right triangles in that rectangle that aren't part of our triangle. When we subtract the area of the right triangles from the area of the rectangle we're left with the area S of our triangle.
That's the cross product in the purest form. When we're away from the origin, a arbitrary triangle with vertices will have the same area as one whose vertex C is translated to the origin.
We set
That's a perfectly useful formula right there. But it's usually multiplied out:
That's the usual form, the sum of cross products. Let's line up our numbers to make it easier.
(1, 2), (3, 4), (−7, 7)
(−7, 7),(1, 2), (3, 4),
[tex]A = \frac 1 2 ( 1(7)-2(-7) + 3(2)-4(1) + -7(4) - (7)(3)
Answer:
x=−2
y=7
Step-by-step explanation:
5x+2y=4
x−3y=−23
In order to solve by elimination, coefficients of one of the variables must be the same in both equations so that the variable will cancel out when one equation is subtracted from the other.
5x+2y=4,x−3y=−23
To make 5x and x equal, multiply all terms on each side of the first equation by 1 and all terms on each side of the second by 5.
5x+2y=4,5x+5(−3)y=5(−23)
Simplify.
5x+2y=4,5x−15y=−115
Subtract 5x−15y=−115 from 5x+2y=4 by subtracting like terms on each side of the equal sign.
5x−5x+2y+15y=4+115
Add 5x to −5x. Terms 5x and −5x cancel out, leaving an equation with only one variable that can be solved.
2y+15y=4+115
Add 2y to 15y.
17y=4+115
Add 4 to 115.
17y=119
Divide both sides by 17.
y=7
Substitute 7 for y in x−3y=−23. Because the resulting equation contains only one variable, you can solve for x directly.
x−3×7=−23
Multiply −3 times 7.
x−21=−23
Add 21 to both sides of the equation.
x=−2
The system is now solved.
x=−2,y=7
Graph if needed:
Answer:
(B)c = StartFraction (3) sine (45 degrees) Over sine (40 degrees) EndFraction
Step-by-step explanation:
In Triangle ABC is shown.
95 degrees
45 degrees.
|AB|=c
|BC|=3.0 cm
Using the Law of Sines
The correct option is B.