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4 years ago

What is the general solution for (cosX + sinX)(1 - 2sinX)=0

1 answer:

7 0

1. square both sides, a straight forward method.
2. hand plot 
3. calculator plot, not recommended.Let Y=sin x + cos x -1 
Y=0, find x=? 
4. Substitute 1=sin^2(x) + cos^2(x) on the right hand side 
Y1=sin^2(x) - sin(x) 
Y2=cos^2(x) - cos(x) 
Y1 + Y2=0, Y1=0, Y2=0, 
a(a-1)=0, so, a=0, a=1, where a=sin(x), or cos(x), 
so x=0, pi/2 
Have a good day!

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The differential equation

Mazyrski [523]

As the question points out, the equation is indeed separable:

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Integrate both sides to get

$2(2y^3+4y^2+3y)=3(x^2+3x)+C$

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3 years ago

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3 years ago

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3 years ago

I need help with #6 please.

Juliette [100K]

9514 1404 393

Answer:

6. (A, B, C) ≈ (112.4°, 29.5°, 38.0°)

7. (a, b, C) ≈ (180.5, 238.5, 145°)

Step-by-step explanation:

My "work" is to make use of a triangle solver calculator. The results are attached. Triangle solvers are available for phone or tablet and on web sites. Many graphing calculators have triangle solvers built in.

We suppose you're to make use of the Law of Sines and the Law of Cosines, as applicable.

6. When 3 sides are given, the Law of Cosines can be used to find the angles. For example, angle A can be found from ...

A = arccos((b² +c² -a²)/(2bc))

A = arccos((8² +10² -15²)/(2·8·10)) = arccos(-61/160) = 112.4°

The other angles can be found by permuting the variables appropriately.

B = arccos((225 +100 -64)/(2·15·10) = arccos(261/300) ≈ 29.5°

The third angle can be found as the supplement to the other two.

C = 180° -112.411° -29.541° = 38.048° ≈ 38.0°

The angles (A, B, C) are about (112.4°, 29.5°, 38.0°).

7. When insufficient information is given for the Law of Cosines, the Law of Sines can be useful. It tells us side lengths are proportional to the sine of the opposite angle. With two angles, we can find the third, and with any side length, we can then find the other side lengths.

C = 180° -A -B = 145°

a = c(sin(A)/sin(C)) = 400·sin(15°)/sin(145°) ≈ 180.49

b = c(sin(B)/sin(C)) = 400·sin(20°)/sin(145°) ≈ 238.52

The measures (a, b, C) are about (180.5, 238.5, 145°).

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3 years ago

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balu736 [363]

Answer:

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Step-by-step explanation:

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4 years ago