Answer: a) Yes, there is enough fance
b) 58.1° and 47.9°
c) The city will not approve, because 1/3 of the area is just 2220.5ft²
Step-by-step explanation:
a) using law of cosines: x is the side we do not know.
x² = 126² + 110² - 2.126.110.cos74°
x² = 20335.3
x = 142.6 ft
So 150 > 142.6, there is enough fance
b) using law of sine:
sin 74/ 142.6 = sinα/126 = sinβ/110
sin 74/ 142.6 = sinα/126
0.006741 = sinα/126
sinα = 0.849
α = sin⁻¹(0.849)
α = 58.1°
sin 74/ 142.6 = sinβ/110
sin 74/ 142.6 = sinβ/110
0.006741 = sinβ/110
sinβ = 0.741
β = sin⁻¹(0.741)
β = 47.9°
Checking: 74+58.1+47.9 = 180° ok
c) Using Heron A² = p(p-a)(p-b)(p-c)
p = a+b+c/2
p=126+110+142.6/2
p=189.3
A² = 189.3(189.3-126)(189.3-110)(189.3-142.6)
A = 6661.5 ft²
1/3 A = 2220.5
So 2300 > 2220.5. The area you want to build is bigger than the area available.
The city will not approve
Well I don't know !
Let's count them.
You can get a 5 if the cubes
fall in any one of these ways:
1 . . . 4
2 . . . 3
3 . . . 2
4 . . . 1
That looks like four possibilities.
Can you think of any others that I missed ?
Answer:
Step-by-step explanation:
![\cos(2x) = \cos^2 x-\sin^2 x = 1-2\sin^2 x \\ \\ \cos(x) = 1-2\sin^2 (\frac{x}{2}) \\ \\ \Rightarrow \sin^2 (\frac{x}{2}) = \dfrac{1-\cos(x)}{2}\\ \\ \sin(\frac{x}{2}) = \pm \sqrt{\dfrac{1-\cos(x)}{2}},\quad x\in [\frac{3\pi }{2},\pi] \Rightarrow \frac{x}{2}\in [\frac{3\pi}{4},\frac{\pi}{2}]\\ \\ \Rightarrow \sin(\frac{x}{2}) > 0 \Rightarrow \sin(\frac{x}{2}) = \sqrt{\dfrac{1-(-\frac{3}{5})}{2}} \Rightarrow \sin(\frac{x}{2}) = \sqrt{\dfrac{8}{10}}=\dfrac{2\sqrt 2}{\sqrt{10}} = \\ \\ =\dfrac{2\sqrt 5}{5}](https://tex.z-dn.net/?f=%5Ccos%282x%29%20%3D%20%5Ccos%5E2%20x-%5Csin%5E2%20x%20%3D%201-2%5Csin%5E2%20x%20%5C%5C%20%5C%5C%20%5Ccos%28x%29%20%3D%201-2%5Csin%5E2%20%28%5Cfrac%7Bx%7D%7B2%7D%29%20%5C%5C%20%5C%5C%20%5CRightarrow%20%5Csin%5E2%20%28%5Cfrac%7Bx%7D%7B2%7D%29%20%3D%20%5Cdfrac%7B1-%5Ccos%28x%29%7D%7B2%7D%5C%5C%20%5C%5C%20%5Csin%28%5Cfrac%7Bx%7D%7B2%7D%29%20%3D%20%5Cpm%20%5Csqrt%7B%5Cdfrac%7B1-%5Ccos%28x%29%7D%7B2%7D%7D%2C%5Cquad%20x%5Cin%20%5B%5Cfrac%7B3%5Cpi%20%7D%7B2%7D%2C%5Cpi%5D%20%5CRightarrow%20%5Cfrac%7Bx%7D%7B2%7D%5Cin%20%5B%5Cfrac%7B3%5Cpi%7D%7B4%7D%2C%5Cfrac%7B%5Cpi%7D%7B2%7D%5D%5C%5C%20%5C%5C%20%5CRightarrow%20%5Csin%28%5Cfrac%7Bx%7D%7B2%7D%29%20%3E%200%20%5CRightarrow%20%5Csin%28%5Cfrac%7Bx%7D%7B2%7D%29%20%3D%20%5Csqrt%7B%5Cdfrac%7B1-%28-%5Cfrac%7B3%7D%7B5%7D%29%7D%7B2%7D%7D%20%5CRightarrow%20%5Csin%28%5Cfrac%7Bx%7D%7B2%7D%29%20%3D%20%5Csqrt%7B%5Cdfrac%7B8%7D%7B10%7D%7D%3D%5Cdfrac%7B2%5Csqrt%202%7D%7B%5Csqrt%7B10%7D%7D%20%3D%20%5C%5C%20%5C%5C%20%3D%5Cdfrac%7B2%5Csqrt%205%7D%7B5%7D)
