Answer:
104°
Step-by-step explanation:

Since perimeter means adding all 4 sides, you divide 86 divided by 4 equals = 21.5. Then do 21.5 + 21.5 which equals 43. And 43 + 43 = 86. So two sides are 21.5, and the other two sides are 43. So 21.5 < 43. 21.5 is the shortest sides. Hope this Helps!
In the half-angle formula for sine and cosine, notice that a plus/minus sign appears in front of each radical (square root). Whether your answer is positive or negative depends on which quadrant the new angle (the half angle) is in
Answer: The correct answer is Choice D, 43 mm.
When you know 2 sides of a triangle, you can find the range for the final side of the triangle.
First, if we subtract 36 - 23 = 13, the third leg must be more than 13. Otherwise, the two smaller legs would not meet to make the third leg.
Second, if we add 36 + 23 = 59, the third leg must be less than 59. Otherwise, the third leg would reach further than the other two legs could reach.
43 is the only number larger than 13 but smaller than 59 in our list.