First we need to identify which trig ratio to use.
One of the known lengths (4.9) is opposite to θ, and the other length (10.6) is adjacent to θ, but we only need half of that length to form a right triangle.
adjacent
=
10.6÷2
adjacent
=
5.3
Hence, we can use the tanratio to solve for θ
tanθ
=
oppositeadjacent
tanratio
tanθ
=
4.95.3
Plug in the values
tanθ
=
0.9243
Use the inverse function for tan on your calculator to get θ by itself
θ
=
tan-1(0.9243)
The inverse of tan is tan-1
θ
=
42.7543
Use the shifttan function on your calculator
θ
=
42°45’15”
Use the degrees function on your calculator
θ
=
42°45’
Rounded to the nearest minute
θ=42°45’
Question 7 of 8
7. Question
Find the area of the Triangle
The given measurements are in units
Round your answer to the nearest whole number
Area =(47)units2
Correct
Correct!
Incorrect
Area of a Triangle Formula
Area =12×a×c×sinB
Remember
Uppercase letters represent angles in the triangle
Lowercase letters represent the side lengths
Labelling the triangle
First, we need to find an angle between two sides with known values.
We can use the Sine Rule to find angle C
asinA
=
csinC
Sine Rule Formula
14sin77°
=
7sinC
Plug in the values
sinC×14
=
7×sin77°
Cross multiply
sinC
=
7×sin77°14
Divide 14 from each side to isolate sinC
sinC
=
6.82114
Simplify
sinC
=
0.487
Use the inverse function for sin on your calculator to get C by itself
C
=
sin-1(0.487)
The inverse of sin is sin-1
C
=
29.155
Use the shift sin function on your calculator
C
=
29.2°
Rounded to one decimal place
Now that we have the value of C, we can get the value of B by subtracting the total value of A and C to 180°, the total interior angle of a triangle
B
=
180°-(A+C)
B
=
180°-(77+29.2)
Plug in the known values
B
=
73.8°
Finally, solve for the area using the Area of a Triangle formula
Area
=
12×a×c×sinB
Area of a Triangle formula
=
12×14×7×sin73.8°
Plug in the known lengths
=
47.0units2
Rounded to one decimal place
The given measurements are in units, so the area is measured as square units
Area=47units2
Question 8 of 8
8. Question
Find the area of the Triangle
The given measurements are in units
Round your answer to the nearest whole number
Area =(92)units2
Correct
Great Work!
Incorrect
Area of a Triangle Formula
Area =12×b×c×sinA
Cosine Rule (finding an angle)
cosA=b2+c2−a22bc
Remember
Uppercase letters represent angles in the triangle
Lowercase letters represent the side lengths
Labelling the triangle
First, we need to find an angle to use for the Area of a Triangle formula
We can use the Cosine Rule (finding an angle) to solve for A
cosA
=
b2+c2−a22bc
Cosine Rule Formula
cosA
=
13.92+142−1622(13.9)(14)
Plug in known values
cosA
=
193.21+196-256389.2
Evaluate
cosA
=
0.342
Use the inverse function for cos on your calculator to get A by itself
A
=
cos-1(0.342)
The inverse of cos is cos-1
A
=
71.094
Use the shift cos function on your calculator
A
=
71.1°
Rounded to one decimal place
Finally, solve for the area using the Area of a Triangle formula
A
=
12×b×c×sinA
Area of a Triangle formula
=
12×13.9×14×sin71.1°
Plug in the known lengths
=
92units2
Rounded to one decimal place
The given measurements are in units, so the area is measured as square units