9x + 5 = 68
9x = 63
x = 7
Cole put seven books on each shelf.
Answer:
7
Step-by-step explanation:
7
Answer:
the law of cosines with ABC
Answer:
C
Step-by-step explanation:
In a Pythagorean triple the square on the longest side is equal to the sum of the squares on the other 2 sides.
A
longest side = 10 ⇒ 10² = 100
6² + 8² = 36 + 64 = 100
A is a Pythagorean triple
B
longest side = 17 ⇒ 17² = 289
8² + 15² = 64 + 225 = 289
B is a Pythagorean triple
C
longest side = 9 ⇒ 9² = 81
5² + 8² = 25 + 64 = 89
89 ≠ 81
C is not a Pythagorean triple
D
longest side = 13 ⇒ 13² = 169
5² + 12² = 25 + 144 = 169
D is a Pythagorean triple
The Law of Cosines features the 3 side lengths of a triangle, plus the measure of the angle opposite one of those sides.
We want angle x, which is opposite the side of length 39.
Then: a^2 = b^2 - 2ab cos C becomes 39^2 = 36^2 + 59^2 - 2(36)(59)cos x
or 1521 = 3481 + 1296 - 2(36)(59) cos x
Subtract (3481+1296) from both sides: 1521 - 4777 = -4248cos x
-3256 = -4248cos x
-3256
Then: cosx = --------------- = 0.766
-4248
Solving for x: x = arccos -0.766 = 0.698 radian, or 40 degrees (answer)
