What is the value of 2sin(3arccos(-1/4)) ?

The value of 2sin(3arccos(-1/4)) is -(3sqrt(15))/8

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Popular Trigonometry >

2sin(3arccos(-1/4))

Solution

2 sin (3 arccos (- \frac{1}{4}))

Solution

- \frac{3 15}{8}

Decimal

- 1.45236 \dots

Solution steps

2 sin (3 arccos (- \frac{1}{4}))

Rewrite using trig identities:

sin (3 arccos (- \frac{1}{4})) = 3 sin (arccos (- \frac{1}{4})) - 4 sin^{3} (arccos (- \frac{1}{4}))

sin (3 arccos (- \frac{1}{4}))

Use the following identity:

sin (3 x) = 3 sin (x) - 4 sin^{3} (x)

sin (3 x)

Rewrite using trig identities

sin (3 x)

Rewrite as

= sin (2 x + x)

Use the Angle Sum identity:

sin (s + t) = sin (s) cos (t) + cos (s) sin (t)

= sin (2 x) cos (x) + cos (2 x) sin (x)

Use the Double Angle identity:

sin (2 x) = 2 sin (x) cos (x)

= cos (2 x) sin (x) + cos (x) 2 sin (x) cos (x)

Simplify

cos (2 x) sin (x) + cos (x) \cdot 2 sin (x) cos (x) : sin (x) cos (2 x) + 2 cos^{2} (x) sin (x)

cos (2 x) sin (x) + cos (x) 2 sin (x) cos (x)

cos (x) \cdot 2 sin (x) cos (x) = 2 cos^{2} (x) sin (x)

cos (x) 2 sin (x) cos (x)

Apply exponent rule:

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

cos (x) cos (x) = cos^{1 + 1} (x)

= 2 sin (x) cos^{1 + 1} (x)

Add the numbers:

1 + 1 = 2

= 2 sin (x) cos^{2} (x)

= sin (x) cos (2 x) + 2 cos^{2} (x) sin (x)

= sin (x) cos (2 x) + 2 cos^{2} (x) sin (x)

= sin (x) cos (2 x) + 2 cos^{2} (x) sin (x)

Use the Double Angle identity:

cos (2 x) = 1 - 2 sin^{2} (x)

= (1 - 2 sin^{2} (x)) sin (x) + 2 cos^{2} (x) sin (x)

Use the Pythagorean identity:

cos^{2} (x) + sin^{2} (x) = 1

cos^{2} (x) = 1 - sin^{2} (x)

= (1 - 2 sin^{2} (x)) sin (x) + 2 (1 - sin^{2} (x)) sin (x)

Expand

(1 - 2 sin^{2} (x)) sin (x) + 2 (1 - sin^{2} (x)) sin (x) : - 4 sin^{3} (x) + 3 sin (x)

(1 - 2 sin^{2} (x)) sin (x) + 2 (1 - sin^{2} (x)) sin (x)

= sin (x) (1 - 2 sin^{2} (x)) + 2 sin (x) (1 - sin^{2} (x))

Expand

sin (x) (1 - 2 sin^{2} (x)) : sin (x) - 2 sin^{3} (x)

sin (x) (1 - 2 sin^{2} (x))

Apply the distributive law:

a (b - c) = ab - a c

a = sin (x), b = 1, c = 2 sin^{2} (x)

= sin (x) 1 - sin (x) 2 sin^{2} (x)

= 1 sin (x) - 2 sin^{2} (x) sin (x)

Simplify

1 \cdot sin (x) - 2 sin^{2} (x) sin (x) : sin (x) - 2 sin^{3} (x)

1 sin (x) - 2 sin^{2} (x) sin (x)

1 \cdot sin (x) = sin (x)

1 sin (x)

Multiply:

1 \cdot sin (x) = sin (x)

= sin (x)

2 sin^{2} (x) sin (x) = 2 sin^{3} (x)

2 sin^{2} (x) sin (x)

Apply exponent rule:

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

sin^{2} (x) sin (x) = sin^{2 + 1} (x)

= 2 sin^{2 + 1} (x)

Add the numbers:

2 + 1 = 3

= 2 sin^{3} (x)

= sin (x) - 2 sin^{3} (x)

= sin (x) - 2 sin^{3} (x)

= sin (x) - 2 sin^{3} (x) + 2 (1 - sin^{2} (x)) sin (x)

Expand

2 sin (x) (1 - sin^{2} (x)) : 2 sin (x) - 2 sin^{3} (x)

2 sin (x) (1 - sin^{2} (x))

Apply the distributive law:

a (b - c) = ab - a c

a = 2 sin (x), b = 1, c = sin^{2} (x)

= 2 sin (x) 1 - 2 sin (x) sin^{2} (x)

= 2 \cdot 1 sin (x) - 2 sin^{2} (x) sin (x)

Simplify

2 \cdot 1 \cdot sin (x) - 2 sin^{2} (x) sin (x) : 2 sin (x) - 2 sin^{3} (x)

2 \cdot 1 sin (x) - 2 sin^{2} (x) sin (x)

2 \cdot 1 \cdot sin (x) = 2 sin (x)

2 \cdot 1 sin (x)

Multiply the numbers:

2 \cdot 1 = 2

= 2 sin (x)

2 sin^{2} (x) sin (x) = 2 sin^{3} (x)

2 sin^{2} (x) sin (x)

Apply exponent rule:

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

sin^{2} (x) sin (x) = sin^{2 + 1} (x)

= 2 sin^{2 + 1} (x)

Add the numbers:

2 + 1 = 3

= 2 sin^{3} (x)

= 2 sin (x) - 2 sin^{3} (x)

= 2 sin (x) - 2 sin^{3} (x)

= sin (x) - 2 sin^{3} (x) + 2 sin (x) - 2 sin^{3} (x)

Simplify

sin (x) - 2 sin^{3} (x) + 2 sin (x) - 2 sin^{3} (x) : - 4 sin^{3} (x) + 3 sin (x)

sin (x) - 2 sin^{3} (x) + 2 sin (x) - 2 sin^{3} (x)

Group like terms

= - 2 sin^{3} (x) - 2 sin^{3} (x) + sin (x) + 2 sin (x)

Add similar elements:

- 2 sin^{3} (x) - 2 sin^{3} (x) = - 4 sin^{3} (x)

= - 4 sin^{3} (x) + sin (x) + 2 sin (x)

Add similar elements:

sin (x) + 2 sin (x) = 3 sin (x)

= - 4 sin^{3} (x) + 3 sin (x)

= - 4 sin^{3} (x) + 3 sin (x)

= - 4 sin^{3} (x) + 3 sin (x)

= 3 sin (x) - 4 sin^{3} (x)

= 3 sin (arccos (- \frac{1}{4})) - 4 sin^{3} (arccos (- \frac{1}{4}))

= 2 (3 sin (arccos (- \frac{1}{4})) - 4 sin^{3} (arccos (- \frac{1}{4})))

Rewrite using trig identities:

sin (arccos (- \frac{1}{4})) = \frac{15}{4}

sin (arccos (- \frac{1}{4}))

Rewrite using trig identities:

sin (arccos (- \frac{1}{4})) = 1 - (- \frac{1}{4})^{2}

Use the following identity:

sin (arccos (x)) = 1 - x^{2}

= 1 - (- \frac{1}{4})^{2}

= 1 - (- \frac{1}{4})^{2}

Simplify

= \frac{15}{4}

= 2 3 \cdot \frac{15}{4} - 4 (\frac{15}{4})^{3}

Simplify

2 3 \cdot \frac{15}{4} - 4 (\frac{15}{4})^{3} : - \frac{3 15}{8}

2 3 \cdot \frac{15}{4} - 4 (\frac{15}{4})^{3}

3 \cdot \frac{15}{4} = \frac{3 15}{4}

3 \cdot \frac{15}{4}

Multiply fractions:

a \cdot \frac{b}{c} = \frac{a \cdot b}{c}

= \frac{15 \cdot 3}{4}

4 (\frac{15}{4})^{3} = \frac{15 15}{16}

4 (\frac{15}{4})^{3}

(\frac{15}{4})^{3} = \frac{15 15}{4 ^{3}}

(\frac{15}{4})^{3}

Apply exponent rule:

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

= \frac{( 15 ) ^{3}}{4 ^{3}}

(15)^{3} : 1 5^{\frac{3}{2}}

Apply radical rule:

a = a^{\frac{1}{2}}

= (1 5^{\frac{1}{2}})^{3}

Apply exponent rule:

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

= 1 5^{\frac{1}{2} \cdot 3}

\frac{1}{2} \cdot 3 = \frac{3}{2}

\frac{1}{2} \cdot 3

Multiply fractions:

a \cdot \frac{b}{c} = \frac{a \cdot b}{c}

= \frac{1 \cdot 3}{2}

Multiply the numbers:

1 \cdot 3 = 3

= \frac{3}{2}

= 1 5^{\frac{3}{2}}

= \frac{1 5 ^{\frac{3}{2}}}{4 ^{3}}

1 5^{\frac{3}{2}} = 1515

1 5^{\frac{3}{2}}

1 5^{\frac{3}{2}} = 1 5^{1 + \frac{1}{2}}

= 1 5^{1 + \frac{1}{2}}

Apply exponent rule:

x^{a + b} = x^{a} x^{b}

= 1 5^{1} \cdot 1 5^{\frac{1}{2}}

Refine

= 1515

= \frac{15 15}{4 ^{3}}

= 4 \cdot \frac{15 15}{4 ^{3}}

Multiply fractions:

a \cdot \frac{b}{c} = \frac{a \cdot b}{c}

= \frac{15 15 \cdot 4}{4 ^{3}}

Multiply the numbers:

15 \cdot 4 = 60

= \frac{60 15}{4 ^{3}}

Factor

60 : 2^{2} \cdot 3 \cdot 5

Factor

60 = 2^{2} \cdot 3 \cdot 5

Factor

4^{3} : 2^{6}

Factor

4 = 2^{2}

= (2^{2})^{3}

Simplify

(2^{2})^{3} : 2^{6}

(2^{2})^{3}

Apply exponent rule:

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

= 2^{2 \cdot 3}

Multiply the numbers:

2 \cdot 3 = 6

= 2^{6}

= 2^{6}

= \frac{2 ^{2} \cdot 3 \cdot 5 15}{2 ^{6}}

Cancel

\frac{2 ^{2} \cdot 3 \cdot 5 15}{2 ^{6}} : \frac{3 \cdot 5 15}{2 ^{4}}

\frac{2 ^{2} \cdot 3 \cdot 5 15}{2 ^{6}}

Apply exponent rule:

\frac{x ^{a}}{x ^{b}} = \frac{1}{x ^{b - a}}

\frac{2 ^{2}}{2 ^{6}} = \frac{1}{2 ^{6 - 2}}

= \frac{3 \cdot 5 15}{2 ^{6 - 2}}

Subtract the numbers:

6 - 2 = 4

= \frac{3 \cdot 5 15}{2 ^{4}}

= \frac{3 \cdot 5 15}{2 ^{4}}

Multiply the numbers:

3 \cdot 5 = 15

= \frac{15 15}{2 ^{4}}

2^{4} = 16

= \frac{15 15}{16}

= 2 (\frac{3 15}{4} - \frac{15 15}{16})

Join

\frac{15 \cdot 3}{4} - \frac{15 15}{16} : - \frac{3 15}{16}

\frac{15 \cdot 3}{4} - \frac{15 15}{16}

Least Common Multiplier of

4, 16 : 16

4, 16

Least Common Multiplier (LCM)

Prime factorization of

4 : 2 \cdot 2

4

4

divides by

24 = 2 \cdot 2

= 2 \cdot 2

Prime factorization of

16 : 2 \cdot 2 \cdot 2 \cdot 2

16

16

divides by

216 = 8 \cdot 2

= 2 \cdot 8

8

divides by

28 = 4 \cdot 2

= 2 \cdot 2 \cdot 4

4

divides by

24 = 2 \cdot 2

= 2 \cdot 2 \cdot 2 \cdot 2

Multiply each factor the greatest number of times it occurs in either

4

16

= 2 \cdot 2 \cdot 2 \cdot 2

Multiply the numbers:

2 \cdot 2 \cdot 2 \cdot 2 = 16

= 16

Adjust Fractions based on the LCM

Multiply each numerator by the same amount needed to multiply its

corresponding denominator to turn it into the LCM

16

For

\frac{15 \cdot 3}{4} :

multiply the denominator and numerator by

4

\frac{15 \cdot 3}{4} = \frac{15 \cdot 3 \cdot 4}{4 \cdot 4} = \frac{12 15}{16}

= \frac{12 15}{16} - \frac{15 15}{16}

Since the denominators are equal, combine the fractions:

\frac{a}{c} \pm \frac{b}{c} = \frac{a \pm b}{c}

= \frac{12 15 - 15 15}{16}

Add similar elements:

1215 - 1515 = - 315

= \frac{- 3 15}{16}

Apply the fraction rule:

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

= - \frac{3 15}{16}

= 2 (- \frac{3 15}{16})

Remove parentheses:

(- a) = - a

= - 2 \cdot \frac{3 15}{16}

Multiply fractions:

a \cdot \frac{b}{c} = \frac{a \cdot b}{c}

= - \frac{3 15 \cdot 2}{16}

Multiply the numbers:

3 \cdot 2 = 6

= - \frac{6 15}{16}

Cancel the common factor:

2

= - \frac{3 15}{8}

= - \frac{3 15}{8}

Popular Examples

Frequently Asked Questions (FAQ)

What is the value of 2sin(3arccos(-1/4)) ?
The value of 2sin(3arccos(-1/4)) is -(3sqrt(15))/8