What is a possible value of sin(theta) when cos2(theta)=0.21
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Answer:
- One proportion to solve is 8/18 = x/8
- Exact answer as a fraction: x = 32/9
- Approximate answer in decimal form: x = 3.556
In reality, the 5's go on forever, but we have to round off somewhere.
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Explanation:
Break up the triangles as your teacher recommends. See the diagram below as to what I mean.
The smaller triangle has A = 8 as the horizontal side, and B = x as the vertical side
The larger triangle has C = 10+8 = 18 as the horizontal aside, and D = 8 as the vertical side.
We can form the proportion A/C = B/D.
A/C connects the horizontal sides (small/large) while B/D has the vertical sides tied together. The order of division is the same small over large. You could do large over small, but make sure you keep both sides consistent.
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Let's solve for x
A/C = B/D
8/18 = x/8
8*8 = 18*x .... cross multiply
64 = 18x
18x = 64
x = 64/18 .... divide both sides by 18
x = 32/9 exactly in fraction form
x = 3.556 approximately in decimal form
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Another proportion you can solve is A/B = C/D and you should get the same x value. It's the same as A/C = B/D because the B and C swap places. There are many other approaches you could take using different proportions.
