Answer:
53°
Step-by-step explanation:
17² = 18² + 20² - 2(18)(20) cos Q
289 = 324 + 400 - 720 cos Q
289 = 724 - 720 cos Q
-435 = -720 cos Q
0.6042 = cos Q

Q = 52.83
Answer:
a is an even number and b is an odd number
Step-by-step explanation:
if a is even and b is even then the sum would be even ex.10+6=16. I'd a and b are both odd the sum would be even ex. 13+9=22. one has to be odd and one has to be even for the sum to be odd ex. 5+4=9
Answer:
34
Step-by-step explanation:
Using the normal distribution, it is found that 25.14% of the batteries will last more than 420 hours.
<h3>Normal Probability Distribution</h3>
The z-score of a measure X of a normally distributed variable with mean
and standard deviation
is given by:

- The z-score measures how many standard deviations the measure is above or below the mean.
- Looking at the z-score table, the p-value associated with this z-score is found, which is the percentile of X.
In this problem, we have that the mean and the standard deviation are given, respectively, by:
.
The proportion of the batteries will last more than 420 hours is <u>one subtracted by the p-value of Z when X = 420</u>, hence:


Z = 0.67
Z = 0.67 has a p-value of 0.7486.
1 - 0.7486 = 0.2514.
0.2514 = 25.14% of the batteries will last more than 420 hours.
More can be learned about the normal distribution at brainly.com/question/24663213
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Easy peasy, this is a representation of differnce of 2 perfect squares
a^2-b^2=(a-b)(a+b)