Use trigonometry
sin 42 = a / 21
a = 21 sin 42 = 14.05
This isn't a math question and should be in the science section. However, I will still answer the question. The answer is choice B.
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Here's a further breakdown
A. False. The radiation or energy from the sun can travel through air or else you wouldn't feel the sun's rays. Also, plant life wouldn't be alive without that energy going through the air.
B. True. The rays travel through a vacuum of space. If they couldn't travel through space, then the same problem comes up as in choice A: the issue of not feeling the sun's rays.
C. False. They rays have different frequencies. Because there are many wavelengths (see choice D below), this means there are different frequencies. Recall that f = 1/w where f is the frequency and w is the wavelength.
D. False. The rays are made of different wavelengths. The visible light portion is what we can see, though there is a lot more to the electromagnetic spectrum (eg: ultraviolet light).
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So once again, the answer is choice B
Answer:
approximation is often useful when it is not a very good one
Answer:
(4, 5 )
Step-by-step explanation:
x + y = 9 → (1)
x - y = - 1 → (2)
adding the 2 equations term by term will eliminate y
2x + 0 = 8
2x = 8 ( divide both sides by 2 )
x = 4
substitute x = 4 into either of the 2 equations and solve for y
substituting into (1)
4 + y = 9 ( subtract 4 from both sides )
y = 5
solution is (4, 5 )
