What is the value of sin(165)cos(75) ?

The value of sin(165)cos(75) is (2-sqrt(3))/4

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sin(165)cos(75)

sin (16 5^{\circ}) cos (7 5^{\circ})

\frac{2 - 3}{4}

Decimal Notation

0.06698 \dots

Solution steps

sin (16 5^{\circ}) cos (7 5^{\circ})

Rewrite using trig identities:

sin (16 5^{\circ}) = sin (1 5^{\circ})

sin (16 5^{\circ})

Use the basic trigonometric identity:

sin (x) = sin (18 0^{\circ} - x)

= sin (18 0^{\circ} - 16 5^{\circ})

Simplify

= sin (1 5^{\circ})

= sin (1 5^{\circ}) cos (7 5^{\circ})

Rewrite using trig identities:

\frac{sin ( 9 0 ^{\circ} ) - sin ( 6 0 ^{\circ} )}{2}

cos (7 5^{\circ}) sin (1 5^{\circ})

Use the Product to Sum identity:

sin (s) cos (t) = \frac{1}{2} (sin (s + t) + sin (s - t))

= \frac{1}{2} (sin (1 5^{\circ} + 7 5^{\circ}) + sin (1 5^{\circ} - 7 5^{\circ}))

Simplify

= \frac{sin ( 9 0 ^{\circ} ) + sin ( - 6 0 ^{\circ} )}{2}

Use the following property:

sin (- x) = - sin (x)

sin (- 6 0^{\circ}) = - sin (6 0^{\circ})

= \frac{sin ( 9 0 ^{\circ} ) - sin ( 6 0 ^{\circ} )}{2}

= \frac{sin ( 9 0 ^{\circ} ) - sin ( 6 0 ^{\circ} )}{2}

Use the following trivial identity:

sin (9 0^{\circ}) = 1

sin (9 0^{\circ})

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}

= 1

Use the following trivial identity:

sin (6 0^{\circ}) = \frac{3}{2}

sin (6 0^{\circ})

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{3}{2}

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

Simplify

\frac{1 - \frac{3}{2}}{2} : \frac{2 - 3}{4}

\frac{1 - \frac{3}{2}}{2}

Join

1 - \frac{3}{2} : \frac{2 - 3}{2}

1 - \frac{3}{2}

Convert element to fraction:

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

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

Multiply the numbers:

1 \cdot 2 = 2

= \frac{2 - 3}{2}

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

Apply the fraction rule:

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

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

Multiply the numbers:

2 \cdot 2 = 4

= \frac{2 - 3}{4}

= \frac{2 - 3}{4}

2 + sin (\frac{3 π}{4})

arcsin (sec (π))

sin (3 5^{\circ}) cos (5 5^{\circ}) + cos (3 5^{\circ}) sin (5 5^{\circ})

\frac{tan ( 7 1 ^{\circ} ) - tan ( 1 1 ^{\circ} )}{1 + tan ( 7 1 ^{\circ} ) tan ( 1 1 ^{\circ} )}

sin_{- 1} (1)

What is the value of sin(165)cos(75) ?
The value of sin(165)cos(75) is (2-sqrt(3))/4