Question

Please help

Answer 1

Answer: 21

Step-by-step explanation:

law of cosines states that x^2 = y^2 + z^2 - 2yzcos<X

so x^2 = 21^2 + 4^2 - (2*21*4*cos(80)) = 457 - 29.1729 = 427.8271

x = 20.6840 which rounds to 21

Answer 2

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)