Answer:
a = 19.451838 ≈ 20
Explanation:
==>Given:
∆ABC with,
<A = 108°
AB = c = 11
AC = b = 13
BC = a = ?
==>Required:
Length of a
==>Solution:
Given 2 sides and a measure of 1 angle, let's find the length of a using the Cosine rule:
a² = b² + c² – 2bc cos(A)
Where a = ?
b = 13
c = 11
A = 108°
Thus,
a² = 13² + 11²- 2(13 × 11) × cos(108)
a² = 169 + 121 - 2(143) × cos(108)
a² = 290 - 286 × (-0.3090)
a² = 290 + 88.374
a² = 378.374
a = √378.374
a = 19.451838 ≈ 20