Question

Could someone help i’ll mark brainliest! please explain too

Answer 1

Answer:

C. 8

Step-by-step explanation:

I almost thought this was going to be Pythagorean Theorem, but no.

Use Cosine Law:

cos θ =  $\frac{10^2 + 21^2 - 17^2}{2(10)(21)}$

θ = cos−1(0.6)

θ = 53.130...

Now use the SOHCAHTOA ratio for sine ($\frac{opposite}{hypotenuse}$) to find x now that you have one angle:

sin θ = $\frac{x}{10}$

x = 10sinθ (θ isn't needed to be written out as it is shown in the equation above)

x = 8