Answer:
x = 21 (Appropriately)
Step-by-step explanation:
Cosine rule states:
a² = b² + c² - 2ab Cos A
b² = a² + c² - 2ac Cos B
c² = a² + c² - 2ab Cos C
Where:
a, b, c are the side lengths
A,B,C are the angles.
We'll take A, B, C as X, Y, Z
and
a,b,c as x,y,z
LET'S FIRE ON!
From the question:
x = ??
y = 21
z = 4
X = 80°
Therefore:
x² = y² + z² - 2yz Cos X
x² = 21² + 4² - 2*21*4 Cos 80°
x²= 441 + 16 - 168 Cos 80°
x² = 457 - 168 * 0.174
x²= 457 - 29.232
x²= 427.768
x= √ 427.768
x = 20.683
x = 21 (Appropriately)
