Answer:
7
Step-by-step explanation:
\underline{\text{Solution Method 2:}}
Solution Method 2:
Use original formula
a^2=b^2+c^2-2bc\cos A
a
2
=b
2
+c
2
−2bccosA
From reference sheet.
\text{Since we are finding }\angle M\text{,}
Since we are finding ∠M,
\text{plug in }2.3\text{ for side }a:
plug in 2.3 for side a:
Opposit the angle we want
2.3^2 = 6.6^2+8.7^2-2(6.6)(8.7)\cos M
2.3
2
=6.6
2
+8.7
2
−2(6.6)(8.7)cosM
Plug in values. Side "a" is opposite the wanted angle.
5.29 = 43.56+75.69-114.84\cos M
5.29=43.56+75.69−114.84cosM
Square sides.
5.29 =
5.29=
\,\,\color{white}{-} 119.25-114.84\cos M
−119.25−114.84cosM
Add.
-119.25=
−119.25=
\,\,-119.25
−119.25
-113.96=
−113.96=
\,\,-114.84\cos M
−114.84cosM
\frac{-113.96}{-114.84}=\cos M
−114.84
−113.96
=cosM
Divide to solve for cos(A).
M= \cos^{-1}(\frac{-113.96}{-114.84})\approx7.098\approx 7^{\circ}
M=cos
−1
(
−114.84
−113.96
)≈7.098≈7
∘
