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)
905=5a
905/5=5a/5
181=a
HOPE THIS HELPS!!!!!!!!!!
Answer and Step-by-step explanation: <u>Standard</u> <u>form</u> of a quadratic equation is expressed as: y=ax²+bx+c, while <u>vertex</u> <u>form</u> is written as:
y=a(x-h)²+k.
The similarities between standard and vertex forms is that they show if the graph of the equation has a <u>minimum</u> (when a>0) or <u>maximum</u> (a<0) and it's easier to determine the y-intercept: for standard, the value of c is the intercept; for vertex, the value k is the intercept.
The advantage of standard form is that you can determine the product and sum of the equation's roots, which is a method to determine them.
The advantages of vertex form are: easier to find the vertex of the graph, which is the pair (h,k) and the axis of symmetry, which is the value of h.
Exterior angles are complementary to the opposite interior angle
For question 4 the answer is yes and for question 5 the answer is false
