Step-by-step explanation:
<u>Answer(1):</u>
Law of Cosines.
<u>Answer(2):</u>
since side "c" is missing so we will write formula used for side "c"

<u>Answer(3):</u>
First lets write both sine and cosine formulas:
Check the attached picture for the list of formulas:
From given picture we see that two angles A and B are missing. Also 1 side "c" is missing.
Sine formula uses two angles while cosine formula uses only one angles.
Hence cosine formula will be best choice to find the missing values.
Answer:
angles in a triangle add up to 180°
5:12:13 = 30
180 ÷ 30 = 6
6 × 5 = 30°
6 × 12 = 72°
6 × 13 = 78°
angles = 30°, 72°, 78°
8-4=4
9-6=3
Use Pythagorean theorem.
The nearest tenth is 5.
So the answer is point D.)