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Popular >

sin^3(o)=4sin(o)sin^2(o)sin^4(o)

Solution

sin^{3} (o) = 4 sin (o) sin^{2} (o) sin^{4} (o)

Solution

o = 2 πn, o = π + 2 πn, o = \frac{5 π}{4} + 2 πn, o = \frac{7 π}{4} + 2 πn, o = \frac{π}{4} + 2 πn, o = \frac{3 π}{4} + 2 πn

Degrees

o = 0^{\circ} + 36 0^{\circ} n, o = 18 0^{\circ} + 36 0^{\circ} n, o = 22 5^{\circ} + 36 0^{\circ} n, o = 31 5^{\circ} + 36 0^{\circ} n, o = 4 5^{\circ} + 36 0^{\circ} n, o = 13 5^{\circ} + 36 0^{\circ} n

Solution steps

sin^{3} (o) = 4 sin (o) sin^{2} (o) sin^{4} (o)

Solve by substitution

sin^{3} (o) = 4 sin (o) sin^{2} (o) sin^{4} (o)

Let:

sin (o) = u

u^{3} = 4 u u^{2} u^{4}

u^{3} = 4 u u^{2} u^{4} : u = 0, u = i \frac{1}{2}, u = - i \frac{1}{2}, u = - \frac{2}{2}, u = \frac{2}{2}

u^{3} = 4 u u^{2} u^{4}

Switch sides

4 u u^{2} u^{4} = u^{3}

Move

u^{3}

to the left side

4 u u^{2} u^{4} = u^{3}

Subtract

u^{3}

from both sides

4 u u^{2} u^{4} - u^{3} = u^{3} - u^{3}

Simplify

4 u^{7} - u^{3} = 0

4 u^{7} - u^{3} = 0

Factor

4 u^{7} - u^{3} : u^{3} (2 u^{2} + 1) (2 u + 1) (2 u - 1)

4 u^{7} - u^{3}

Factor out common term

u^{3} : u^{3} (4 u^{4} - 1)

4 u^{7} - u^{3}

Apply exponent rule:

a^{b + c} = a^{b} a^{c}

u^{7} = u^{4} u^{3}

= 4 u^{4} u^{3} - u^{3}

Factor out common term

u^{3}

= u^{3} (4 u^{4} - 1)

= u^{3} (4 u^{4} - 1)

Factor

4 u^{4} - 1 : (2 u^{2} + 1) (2 u + 1) (2 u - 1)

4 u^{4} - 1

Rewrite

4 u^{4} - 1

(2 u^{2})^{2} - 1^{2}

4 u^{4} - 1

Rewrite

4

2^{2}

= 2^{2} u^{4} - 1

Rewrite

1

1^{2}

= 2^{2} u^{4} - 1^{2}

Apply exponent rule:

a^{b c} = (a^{b})^{c}

u^{4} = (u^{2})^{2}

= 2^{2} (u^{2})^{2} - 1^{2}

Apply exponent rule:

a^{m} b^{m} = (ab)^{m}

2^{2} (u^{2})^{2} = (2 u^{2})^{2}

= (2 u^{2})^{2} - 1^{2}

= (2 u^{2})^{2} - 1^{2}

Apply Difference of Two Squares Formula:

x^{2} - y^{2} = (x + y) (x - y)

(2 u^{2})^{2} - 1^{2} = (2 u^{2} + 1) (2 u^{2} - 1)

= (2 u^{2} + 1) (2 u^{2} - 1)

Factor

2 u^{2} - 1 : (2 u + 1) (2 u - 1)

2 u^{2} - 1

Rewrite

2 u^{2} - 1

(2 u)^{2} - 1^{2}

2 u^{2} - 1

Apply radical rule:

a = (a)^{2}

2 = (2)^{2}

= (2)^{2} u^{2} - 1

Rewrite

1

1^{2}

= (2)^{2} u^{2} - 1^{2}

Apply exponent rule:

a^{m} b^{m} = (ab)^{m}

(2)^{2} u^{2} = (2 u)^{2}

= (2 u)^{2} - 1^{2}

= (2 u)^{2} - 1^{2}

Apply Difference of Two Squares Formula:

x^{2} - y^{2} = (x + y) (x - y)

(2 u)^{2} - 1^{2} = (2 u + 1) (2 u - 1)

= (2 u + 1) (2 u - 1)

= (2 u^{2} + 1) (2 u + 1) (2 u - 1)

= u^{3} (2 u^{2} + 1) (2 u + 1) (2 u - 1)

u^{3} (2 u^{2} + 1) (2 u + 1) (2 u - 1) = 0

Using the Zero Factor Principle:

ab = 0

then

a = 0

b = 0

u = 0 or 2 u^{2} + 1 = 0 or 2 u + 1 = 0 or 2 u - 1 = 0

Solve

2 u^{2} + 1 = 0 : u = i \frac{1}{2}, u = - i \frac{1}{2}

2 u^{2} + 1 = 0

Move

1

to the right side

2 u^{2} + 1 = 0

Subtract

1

from both sides

2 u^{2} + 1 - 1 = 0 - 1

Simplify

2 u^{2} = - 1

2 u^{2} = - 1

Divide both sides by

2

2 u^{2} = - 1

Divide both sides by

2

\frac{2 u ^{2}}{2} = \frac{- 1}{2}

Simplify

u^{2} = - \frac{1}{2}

u^{2} = - \frac{1}{2}

For

x^{2} = f (a)

the solutions are

x = f (a), - f (a)

u = - \frac{1}{2}, u = - - \frac{1}{2}

Simplify

- \frac{1}{2} : i \frac{1}{2}

- \frac{1}{2}

Apply radical rule:

- a = - 1 a

- \frac{1}{2} = - 1 \frac{1}{2}

= - 1 \frac{1}{2}

Apply imaginary number rule:

- 1 = i

= i \frac{1}{2}

Simplify

- - \frac{1}{2} : - i \frac{1}{2}

- - \frac{1}{2}

Simplify

- \frac{1}{2} : i \frac{1}{2}

- \frac{1}{2}

Apply radical rule:

- a = - 1 a

- \frac{1}{2} = - 1 \frac{1}{2}

= - 1 \frac{1}{2}

Apply imaginary number rule:

- 1 = i

= i \frac{1}{2}

= - i \frac{1}{2}

u = i \frac{1}{2}, u = - i \frac{1}{2}

Solve

2 u + 1 = 0 : u = - \frac{2}{2}

2 u + 1 = 0

Move

1

to the right side

2 u + 1 = 0

Subtract

1

from both sides

2 u + 1 - 1 = 0 - 1

Simplify

2 u = - 1

2 u = - 1

Divide both sides by

2

2 u = - 1

Divide both sides by

2

\frac{2 u}{2} = \frac{- 1}{2}

Simplify

\frac{2 u}{2} = \frac{- 1}{2}

Simplify

\frac{2 u}{2} : u

\frac{2 u}{2}

Cancel the common factor:

2

= u

Simplify

\frac{- 1}{2} : - \frac{2}{2}

\frac{- 1}{2}

Apply the fraction rule:

\frac{- a}{b} = - \frac{a}{b}

= - \frac{1}{2}

Rationalize

- \frac{1}{2} : - \frac{2}{2}

- \frac{1}{2}

Multiply by the conjugate

\frac{2}{2}

= - \frac{1 \cdot 2}{2 2}

1 \cdot 2 = 2

22 = 2

22

Apply radical rule:

a a = a

22 = 2

= 2

= - \frac{2}{2}

= - \frac{2}{2}

u = - \frac{2}{2}

u = - \frac{2}{2}

u = - \frac{2}{2}

Solve

2 u - 1 = 0 : u = \frac{2}{2}

2 u - 1 = 0

Move

1

to the right side

2 u - 1 = 0

Add

1

to both sides

2 u - 1 + 1 = 0 + 1

Simplify

2 u = 1

2 u = 1

Divide both sides by

2

2 u = 1

Divide both sides by

2

\frac{2 u}{2} = \frac{1}{2}

Simplify

\frac{2 u}{2} = \frac{1}{2}

Simplify

\frac{2 u}{2} : u

\frac{2 u}{2}

Cancel the common factor:

2

= u

Simplify

\frac{1}{2} : \frac{2}{2}

\frac{1}{2}

Multiply by the conjugate

\frac{2}{2}

= \frac{1 \cdot 2}{2 2}

1 \cdot 2 = 2

22 = 2

22

Apply radical rule:

a a = a

22 = 2

= 2

= \frac{2}{2}

u = \frac{2}{2}

u = \frac{2}{2}

u = \frac{2}{2}

The solutions are

u = 0, u = i \frac{1}{2}, u = - i \frac{1}{2}, u = - \frac{2}{2}, u = \frac{2}{2}

Substitute back

u = sin (o)

sin (o) = 0, sin (o) = i \frac{1}{2}, sin (o) = - i \frac{1}{2}, sin (o) = - \frac{2}{2}, sin (o) = \frac{2}{2}

sin (o) = 0, sin (o) = i \frac{1}{2}, sin (o) = - i \frac{1}{2}, sin (o) = - \frac{2}{2}, sin (o) = \frac{2}{2}

sin (o) = 0 : o = 2 πn, o = π + 2 πn

sin (o) = 0

General solutions for

sin (o) = 0

sin (x)

periodicity table with

2 πn

cycle:

x 0 \frac{π}{6} \frac{π}{4} \frac{π}{3} \frac{π}{2} \frac{2 π}{3} \frac{3 π}{4} \frac{5 π}{6} sin (x) 0 \frac{1}{2} \frac{2}{2} \frac{3}{2} 1 \frac{3}{2} \frac{2}{2} \frac{1}{2} x π \frac{7 π}{6} \frac{5 π}{4} \frac{4 π}{3} \frac{3 π}{2} \frac{5 π}{3} \frac{7 π}{4} \frac{11 π}{6} sin (x) 0 - \frac{1}{2} - \frac{2}{2} - \frac{3}{2} - 1 - \frac{3}{2} - \frac{2}{2} - \frac{1}{2}

o = 0 + 2 πn, o = π + 2 πn

o = 0 + 2 πn, o = π + 2 πn

Solve

o = 0 + 2 πn : o = 2 πn

o = 0 + 2 πn

0 + 2 πn = 2 πn

o = 2 πn

o = 2 πn, o = π + 2 πn

sin (o) = i \frac{1}{2} :

No Solution

sin (o) = i \frac{1}{2}

No Solution

sin (o) = - i \frac{1}{2} :

No Solution

sin (o) = - i \frac{1}{2}

No Solution

sin (o) = - \frac{2}{2} : o = \frac{5 π}{4} + 2 πn, o = \frac{7 π}{4} + 2 πn

sin (o) = - \frac{2}{2}

General solutions for

sin (o) = - \frac{2}{2}

sin (x)

periodicity table with

2 πn

cycle:

x 0 \frac{π}{6} \frac{π}{4} \frac{π}{3} \frac{π}{2} \frac{2 π}{3} \frac{3 π}{4} \frac{5 π}{6} sin (x) 0 \frac{1}{2} \frac{2}{2} \frac{3}{2} 1 \frac{3}{2} \frac{2}{2} \frac{1}{2} x π \frac{7 π}{6} \frac{5 π}{4} \frac{4 π}{3} \frac{3 π}{2} \frac{5 π}{3} \frac{7 π}{4} \frac{11 π}{6} sin (x) 0 - \frac{1}{2} - \frac{2}{2} - \frac{3}{2} - 1 - \frac{3}{2} - \frac{2}{2} - \frac{1}{2}

o = \frac{5 π}{4} + 2 πn, o = \frac{7 π}{4} + 2 πn

o = \frac{5 π}{4} + 2 πn, o = \frac{7 π}{4} + 2 πn

sin (o) = \frac{2}{2} : o = \frac{π}{4} + 2 πn, o = \frac{3 π}{4} + 2 πn

sin (o) = \frac{2}{2}

General solutions for

sin (o) = \frac{2}{2}

sin (x)

periodicity table with

2 πn

cycle:

x 0 \frac{π}{6} \frac{π}{4} \frac{π}{3} \frac{π}{2} \frac{2 π}{3} \frac{3 π}{4} \frac{5 π}{6} sin (x) 0 \frac{1}{2} \frac{2}{2} \frac{3}{2} 1 \frac{3}{2} \frac{2}{2} \frac{1}{2} x π \frac{7 π}{6} \frac{5 π}{4} \frac{4 π}{3} \frac{3 π}{2} \frac{5 π}{3} \frac{7 π}{4} \frac{11 π}{6} sin (x) 0 - \frac{1}{2} - \frac{2}{2} - \frac{3}{2} - 1 - \frac{3}{2} - \frac{2}{2} - \frac{1}{2}

o = \frac{π}{4} + 2 πn, o = \frac{3 π}{4} + 2 πn

o = \frac{π}{4} + 2 πn, o = \frac{3 π}{4} + 2 πn

Combine all the solutions

o = 2 πn, o = π + 2 πn, o = \frac{5 π}{4} + 2 πn, o = \frac{7 π}{4} + 2 πn, o = \frac{π}{4} + 2 πn, o = \frac{3 π}{4} + 2 πn

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