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: The toy should be 2.4 inches tall
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Explanation:
First convert 6 ft to inches
6 ft = (6 ft)*(12 in/1 ft) = (6*12) inches = 72 inches
So, 6 ft = 72 inches
The toy is manufactured with a scale of 1:30 meaning that the toy is 1 unit tall compared to the soldier which is 30 units tall. The soldier is 30 times taller than the toy. We can therefore form the ratio
1/30 = x/72
where x is the height of the toy soldier in inches
Cross multiply and solve for x
1/30 = x/72
1*72 = 30*x
72 = 30*x
72/30 = 30*x/30
72/30 = x
x = 72/30
x = 12/5
x = 2.4
So the toy should be 2.4 inches tall.
Note how 30 times 2.4 gives us
30*2.4 = 72
which fits with the theme that the real soldier is 30 times taller than the toy counter part.
Answer:
angle b = 40 degrees
Step-by-step explanation:
Because angle a + angle b = 90 degrees
50 + angle b = 90
angle b = 90 - 50 = 40 degrees.
Answer:
The greater the sample size the better is the estimation. A large sample leads to a more accurate result.
Step-by-step explanation:
Consider the table representing the number of heads and tails for all the number of tosses:
Number of tosses n (HEADS) n (TAILS) Ratio
10 3 7 3 : 7
30 14 16 7 : 8
100 60 40 3 : 2
Compute probability of heads for the tosses as follows:
The probability of heads in case of 10 tosses of a coin is -0.20 away from 50/50.
The probability of heads in case of 30 tosses of a coin is -0.033 away from 50/50.
The probability of heads in case of 100 tosses of a coin is 0.10 away from 50/50.
As it can be seen from the above explanation, that as the sample size is increasing the distance between the expected and observed proportion is decreasing.
This happens because, the greater the sample size the better is the estimation. A large sample leads to a more accurate result.
