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earnstyle [38]
3 years ago
12

Find all solutions to the equation. cos2x + 2 cos x + 1 = 0

Mathematics
1 answer:
yanalaym [24]3 years ago
5 0
For cos(2x) * (2cos(x) + 1) = 0, use the double angle identity for cos(2x), which is cos^2 x - sin^2 x = cos^2 x - (1-cos^2) = 2cos^2 x - 1.
So we have (2cos^2 x - 1)(2cos x + 1) = 0. So 2cos^2 x -1 = 0 or x = 0 and 2pi.
For 2sec^2 x + tan^2 x - 3 = 0, use the identity sec^2 x = tan^2 x + 1, so we have
2(tan^2 x + 1) + tan^2 x - 3 = 0 or
<span>2tan^2 x + tan^2 x - 1 = 0 or
</span>3 tan^2 x = 1.

So x = pi/2, pi/2 + pi = 3pi/2.

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What is the answer to this question
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Triangles abc, dbe, and fbg are all symmetric about the y-axis. what are the coordinates of the centroid?
Drupady [299]

Answer:

The coordinates of the centroid are (0, 5)

Step-by-step explanation:

The coordinates of the centroid of a triangle whose vertices (x1, y1), (x2, y2), and (x3, y3) are (\frac{x1+x2+x3}{3} , \frac{y1+y2+y3}{3})

In Δ ABC

∵ A = (-20, 0), B = (0, 15), C = (20, 0)

∴ x1 = -20, x2 = 0, x3 = 20

∴ y1 = 0, y2 = 15, y3 = 0

∴ The centroid = (\frac{-20+0+20}{3} , \frac{0+15+0}{3}) = (\frac{0}{3} , \frac{15}{3}) = (0, 5)

∴ The coordinates of the centroid of Δ ABC are (0, 5)

In Δ DBE

∵ D = (-15, 0), B = (0, 15), E = (15, 0)

∴ x1 = -15, x2 = 0, x3 = 15

∴ y1 = 0, y2 = 15, y3 = 0

∴ The centroid = (\frac{-15+0+15}{3} , \frac{0+15+0}{3}) = (\frac{0}{3} , \frac{15}{3}) = (0, 5)

∴ The coordinates of the centroid of Δ DBE are (0, 5)

In Δ FBG

∵ F = (-5, 0), B = (0, 15), G = (5, 0)

∴ x1 = -5, x2 = 0, x3 = 5

∴ y1 = 0, y2 = 15, y3 = 0

∴ The centroid = (\frac{-5+0+5}{3} , \frac{0+15+0}{3}) = (\frac{0}{3} , \frac{15}{3}) = (0, 5)

∴ The coordinates of the centroid of Δ FBG are (0, 5)

∵ The three triangles are symmetric about the y-axis

→ That means they have the same centroid and it lies on the y-axis

∴ The coordinates of the centroid are (0, 5)

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