Is sin(x+30)+sqrt(3)cos(x+30)=2cos(x) ?

The answer to whether sin(x+30)+sqrt(3)cos(x+30)=2cos(x) is True

English

Español

Português

Français

Deutsch

Italiano

Русский

中文(简体)

한국어

日本語

Tiếng Việt

עברית

العربية

Popular Trigonometry >

prove sin(x+30)+sqrt(3)cos(x+30)=2cos(x)

Solution

prove

sin (x + 3 0^{\circ}) + 3 cos (x + 3 0^{\circ}) = 2 cos (x)

Solution

True

Solution steps

sin (x + 3 0^{\circ}) + 3 cos (x + 3 0^{\circ}) = 2 cos (x)

Manipulating left side

sin (x + 3 0^{\circ}) + 3 cos (x + 3 0^{\circ})

Rewrite using trig identities

sin (x + 3 0^{\circ})

Use the Angle Sum identity:

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

= sin (x) cos (3 0^{\circ}) + cos (x) sin (3 0^{\circ})

Simplify

sin (x) cos (3 0^{\circ}) + cos (x) sin (3 0^{\circ}) : \frac{3}{2} sin (x) + \frac{1}{2} cos (x)

sin (x) cos (3 0^{\circ}) + cos (x) sin (3 0^{\circ})

Simplify

cos (3 0^{\circ}) : \frac{3}{2}

cos (3 0^{\circ})

Use the following trivial identity:

cos (3 0^{\circ}) = \frac{3}{2}

cos (x)

periodicity table with

36 0^{\circ} n

cycle:

x 0 3 0^{\circ} 4 5^{\circ} 6 0^{\circ} 9 0^{\circ} 12 0^{\circ} 13 5^{\circ} 15 0^{\circ} cos (x) 1 \frac{3}{2} \frac{2}{2} \frac{1}{2} 0 - \frac{1}{2} - \frac{2}{2} - \frac{3}{2} x 18 0^{\circ} 21 0^{\circ} 22 5^{\circ} 24 0^{\circ} 27 0^{\circ} 30 0^{\circ} 31 5^{\circ} 33 0^{\circ} cos (x) - 1 - \frac{3}{2} - \frac{2}{2} - \frac{1}{2} 0 \frac{1}{2} \frac{2}{2} \frac{3}{2}

= \frac{3}{2}

= \frac{3}{2} sin (x) + sin (3 0^{\circ}) cos (x)

Simplify

sin (3 0^{\circ}) : \frac{1}{2}

sin (3 0^{\circ})

Use the following trivial identity:

sin (3 0^{\circ}) = \frac{1}{2}

sin (x)

periodicity table with

36 0^{\circ} n

cycle:

x 0 3 0^{\circ} 4 5^{\circ} 6 0^{\circ} 9 0^{\circ} 12 0^{\circ} 13 5^{\circ} 15 0^{\circ} sin (x) 0 \frac{1}{2} \frac{2}{2} \frac{3}{2} 1 \frac{3}{2} \frac{2}{2} \frac{1}{2} x 18 0^{\circ} 21 0^{\circ} 22 5^{\circ} 24 0^{\circ} 27 0^{\circ} 30 0^{\circ} 31 5^{\circ} 33 0^{\circ} sin (x) 0 - \frac{1}{2} - \frac{2}{2} - \frac{3}{2} - 1 - \frac{3}{2} - \frac{2}{2} - \frac{1}{2}

= \frac{1}{2}

= \frac{3}{2} sin (x) + \frac{1}{2} cos (x)

= \frac{3}{2} sin (x) + \frac{1}{2} cos (x)

= \frac{3}{2} sin (x) + \frac{1}{2} cos (x) + 3 cos (x + 3 0^{\circ})

Rewrite using trig identities

cos (x + 3 0^{\circ})

Use the Angle Sum identity:

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

= cos (x) cos (3 0^{\circ}) - sin (x) sin (3 0^{\circ})

Simplify

cos (x) cos (3 0^{\circ}) - sin (x) sin (3 0^{\circ}) : \frac{3}{2} cos (x) - \frac{1}{2} sin (x)

cos (x) cos (3 0^{\circ}) - sin (x) sin (3 0^{\circ})

Simplify

cos (3 0^{\circ}) : \frac{3}{2}

cos (3 0^{\circ})

Use the following trivial identity:

cos (3 0^{\circ}) = \frac{3}{2}

cos (x)

periodicity table with

36 0^{\circ} n

cycle:

x 0 3 0^{\circ} 4 5^{\circ} 6 0^{\circ} 9 0^{\circ} 12 0^{\circ} 13 5^{\circ} 15 0^{\circ} cos (x) 1 \frac{3}{2} \frac{2}{2} \frac{1}{2} 0 - \frac{1}{2} - \frac{2}{2} - \frac{3}{2} x 18 0^{\circ} 21 0^{\circ} 22 5^{\circ} 24 0^{\circ} 27 0^{\circ} 30 0^{\circ} 31 5^{\circ} 33 0^{\circ} cos (x) - 1 - \frac{3}{2} - \frac{2}{2} - \frac{1}{2} 0 \frac{1}{2} \frac{2}{2} \frac{3}{2}

= \frac{3}{2}

= \frac{3}{2} cos (x) - sin (3 0^{\circ}) sin (x)

Simplify

sin (3 0^{\circ}) : \frac{1}{2}

sin (3 0^{\circ})

Use the following trivial identity:

sin (3 0^{\circ}) = \frac{1}{2}

sin (x)

periodicity table with

36 0^{\circ} n

cycle:

x 0 3 0^{\circ} 4 5^{\circ} 6 0^{\circ} 9 0^{\circ} 12 0^{\circ} 13 5^{\circ} 15 0^{\circ} sin (x) 0 \frac{1}{2} \frac{2}{2} \frac{3}{2} 1 \frac{3}{2} \frac{2}{2} \frac{1}{2} x 18 0^{\circ} 21 0^{\circ} 22 5^{\circ} 24 0^{\circ} 27 0^{\circ} 30 0^{\circ} 31 5^{\circ} 33 0^{\circ} sin (x) 0 - \frac{1}{2} - \frac{2}{2} - \frac{3}{2} - 1 - \frac{3}{2} - \frac{2}{2} - \frac{1}{2}

= \frac{1}{2}

= \frac{3}{2} cos (x) - \frac{1}{2} sin (x)

= \frac{3}{2} cos (x) - \frac{1}{2} sin (x)

= \frac{3}{2} sin (x) + \frac{1}{2} cos (x) + 3 (\frac{3}{2} cos (x) - \frac{1}{2} sin (x))

Simplify

\frac{3}{2} sin (x) + \frac{1}{2} cos (x) + 3 (\frac{3}{2} cos (x) - \frac{1}{2} sin (x)) : 2 cos (x)

\frac{3}{2} sin (x) + \frac{1}{2} cos (x) + 3 (\frac{3}{2} cos (x) - \frac{1}{2} sin (x))

Expand

3 (\frac{3}{2} cos (x) - \frac{1}{2} sin (x)) : \frac{3}{2} cos (x) - \frac{3}{2} sin (x)

3 (\frac{3}{2} cos (x) - \frac{1}{2} sin (x))

Apply the distributive law:

a (b - c) = ab - a c

a = 3, b = \frac{3}{2} cos (x), c = \frac{1}{2} sin (x)

= 3 \frac{3}{2} cos (x) - 3 \frac{1}{2} sin (x)

Simplify

3 \frac{3}{2} cos (x) - 3 \frac{1}{2} sin (x) : \frac{3}{2} cos (x) - \frac{3}{2} sin (x)

3 \frac{3}{2} cos (x) - 3 \frac{1}{2} sin (x)

3 \frac{3}{2} cos (x) = \frac{3}{2} cos (x)

3 \frac{3}{2} cos (x)

Multiply fractions:

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

= \frac{3 3}{2} cos (x)

33 = 3

33

Apply radical rule:

a a = a

33 = 3

= 3

= \frac{3}{2} cos (x)

3 \frac{1}{2} sin (x) = \frac{3}{2} sin (x)

3 \frac{1}{2} sin (x)

Multiply fractions:

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

= \frac{1 \cdot 3}{2} sin (x)

Multiply:

1 \cdot 3 = 3

= \frac{3}{2} sin (x)

= \frac{3}{2} cos (x) - \frac{3}{2} sin (x)

= \frac{3}{2} cos (x) - \frac{3}{2} sin (x)

= \frac{3}{2} sin (x) + \frac{1}{2} cos (x) + \frac{3}{2} cos (x) - \frac{3}{2} sin (x)

Simplify

\frac{3}{2} sin (x) + \frac{1}{2} cos (x) + \frac{3}{2} cos (x) - \frac{3}{2} sin (x) : 2 cos (x)

\frac{3}{2} sin (x) + \frac{1}{2} cos (x) + \frac{3}{2} cos (x) - \frac{3}{2} sin (x)

Group like terms

= \frac{1}{2} cos (x) + \frac{3}{2} cos (x) + \frac{3}{2} sin (x) - \frac{3}{2} sin (x)

Add similar elements:

\frac{1}{2} cos (x) + \frac{3}{2} cos (x) = 2 cos (x)

\frac{1}{2} cos (x) + \frac{3}{2} cos (x)

Factor out common term

cos (x)

= cos (x) (\frac{1}{2} + \frac{3}{2})

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

\frac{1}{2} + \frac{3}{2}

Apply rule

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

= \frac{1 + 3}{2}

Add the numbers:

1 + 3 = 4

= \frac{4}{2}

Divide the numbers:

\frac{4}{2} = 2

= 2

= 2 cos (x)

= 2 cos (x) + \frac{3}{2} sin (x) - \frac{3}{2} sin (x)

Add similar elements:

\frac{3}{2} sin (x) - \frac{3}{2} sin (x) = 0

\frac{3}{2} sin (x) - \frac{3}{2} sin (x)

Factor out common term

sin (x)

= sin (x) (\frac{3}{2} - \frac{3}{2})

\frac{3}{2} - \frac{3}{2} = 0

\frac{3}{2} - \frac{3}{2}

Since the denominators are equal, combine the fractions:

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

= \frac{3 - 3}{2}

Factor

3 - 3 : 0

3 - 3

Factor out common term

3

= 3 (1 - 1)

Refine

= 0

= \frac{0}{2}

Apply rule

\frac{0}{a} = 0, a \neq = 0

= 0

= 0

= 2 cos (x)

= 2 cos (x)

= 2 cos (x)

We showed that the two sides could take the same form

\Rightarrow True

Popular Examples

prove (8csc(-x))/(sec(-x))=-8cot(x)

p ro v e \frac{8 csc ( - x )}{sec ( - x )} = - 8 cot (x)

prove cos(α-β)=cos(α)cos(β)+sin(α)sin(β)

p ro v e cos (α - β) = cos (α) cos (β) + sin (α) sin (β)

prove cos^2(x)-sin^2(x)=1-sin^2(x)

p ro v e cos^{2} (x) - sin^{2} (x) = 1 - sin^{2} (x)

prove sin^3(x)= 3/4 sin(x)-1/4 sin(3x)

p ro v e sin^{3} (x) = \frac{3}{4} sin (x) - \frac{1}{4} sin (3 x)

prove cos^2(x)=(1-sin(x))(1+sin(x))

p ro v e cos^{2} (x) = (1 - sin (x)) (1 + sin (x))

Frequently Asked Questions (FAQ)

Is sin(x+30)+sqrt(3)cos(x+30)=2cos(x) ?
The answer to whether sin(x+30)+sqrt(3)cos(x+30)=2cos(x) is True