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6.40 Solve Problems Using Trigonometry.notebook
1
May 28, 2020
Solutions
Cosine law no right angle, no angleside pair
Sine law no right angle, have an angleside pair
Primary trigonometric ratios have a right angle
Cosine law no right angle, no angleside pair
6.40 Solve Problems Using Trigonometry.notebook
2
May 28, 2020
a)
xsin(C) =
asin(A)
xsin(40) =
6.7sin(80)
x = 6.7sin(40)sin(80)x = 4.373...
A
DC 60Ο
x
6.7 cm
50Ο
<C = 90 50 = 40Ο
<A = 180 40 60
<A = 80Ο
x = 4.4 cm
b)
50Ο
4.5 cmB A
C
a
tan(Θ) =oppadj
tan(50) =4.5a
atan(50) = 4.5
a = 4.5tan(50)
a = 3.7759...
A
DC 60Ο
x
6.7 cm
a
sin(Θ) =opphyp
sin(60) =3.7759
xxsin(60) = 3.7759
x = 3.7759sin(60)
x = 4.3600...x = 4.4 cm
6.40 Solve Problems Using Trigonometry.notebook
3
May 28, 2020
68Ο 56Ο
56Ο68Ο
1.5 km
A
B
CX
tan(Θ) =oppadj
tan(56) = 1.5XC
tan(Θ) =oppadj
tan(68) = 1.5AX
AX = 1.5tan(68) XC =
1.5tan(56)
Angles of depression are measured from the horizontal so they form alternate "Z" angles with the ground
AXtan(68) = 1.5 XCtan(56) = 1.5
AX = 0.606... XC = 1.011...
Width of the crater = 0.606 + 1.011
= 1.6 km
74Ο
17 km
12 kmR D
Ha) Use cosine law to find "d"
d2 = h2 + r2 2hrcos(D)
d2 = 122 + 172 2(12)(17)cos(74)
d2 = 320.5399...
d = √(320.5399...)
d = 17.9036...
d = 18 kmRace distance = 17 + 12 + 18
= 47 km
cos(H) = 2dr
d2 + r2 h2
cos(H) = 2(18)(17)
182 + 172 122
cos(H) = 612469
cos(H) = 0.7663...
H = cos1(0.7663...)H = 39.973...
b)
<H = 40Ο<R = 180 74 40
<R = 66Ο
From the question <D = 74Ο
6.40 Solve Problems Using Trigonometry.notebook
4
May 28, 2020
1.5 m
14 mA
B
C
tan(Θ) =oppadj
tan(C) =1.514
tan(C) = 0.1071...
C = tan1(0.1071...)
C = 6.1155...
C = 6Ο
cos(Θ) =adjhyp
cos(6) =14a
acos(6) = 14
a =14
cos(6)a = 14.077...a = 14.1 m
36Ο
6ΟB
D
E
<E = 84Ο (90Ο 6Ο)
a
b
bsin(B) =
dsin(D)
bsin(36) =
14.1sin(60)
b = 14.1sin(36)sin(60)b = 9.5698...
<D = 180 36 84
<D = 60Ο
The building is 9.6 metres tall
d is "a"
B R
E
45Ο
b
Using the cosine law, find distance "b"
b2 = e2 + r2 2ercos(B)
b2 = 152 + 182 2(15)(18)cos(45)
b2 = 167.163...
b = √(167.163...)
b = 12.929...
b = 12.9 m
15 m
18 m
Now find how long it will take each of them to get to the eucalyptus...
Rocco can run 12.9 m at 1 m/s
TimeR = 12.9 ÷ 1 = 12.9 seconds
Biff can run 18 m at 1.5 m/s
TimeB = 18 ÷ 1.5 = 12 seconds
Speed = DistanceTimeDistanceSpeedTime =
Biff can beat Rocco to the eucalyptus (assuming that there are no obstacles in his way)
6.40 Solve Problems Using Trigonometry.notebook
5
May 28, 2020
6400 km0.0025Ο
x
tan(Θ) =oppadj
tan(0.0025) =6400x
xtan(0.0025) = 6400
x =6400
tan(0.0025)x = 146,677,195.5 km
This compares quite well with the answer of 149,600,000 km from #5
a) b) The measurements are likely to have been taken at around noon (not adjusting for daylight savings) when the sun is at its highest point.