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To determine to measure of the unknown angle, be sure to use the total sum of 180°. If two angles are given, add them together and then subtract from 180°. If two angles are the same and unknown, subtract the known angle from 180° and then divide by 2.
Cross multiply the expression so that we can get
(1+sinx)(1-sinx) = cos^2 x
1 - sin^2 x = cos^2 x
cos^2 x + sin^2 x = 1
since
cos^2 x + sin^2 x = 1
therefore
1 = 1
the two expressions are identical in a trigonometric sense
Answer:
A. $1,710
B. Yes, probably.
Step-by-step explanation:
Assuming that a 10% decrease in energy use leads to a 10% decrease in the electric bill:
We'll want to find the value which is 10% less than the original value, i.e., the bill cost which is 90% of the original bill.
90% = 0.9
Since the original bill was $1900, we can just multiply 1900 by 0.9:

Answer: A bill of $1,710 would equal a 10% decrease.
Since $1,672 is less than that, then they have decreased their energy use by more than 10% which is likely a success.
Answer: Yes, probably.
I would go with D, it looks like it is the most linear out of the rest, Hope it helps:)