What is the value of sin(30)-cos(45) ?

The value of sin(30)-cos(45) is (1-sqrt(2))/2

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sin(30)-cos(45)

sin (3 0^{\circ}) - cos (4 5^{\circ})

\frac{1 - 2}{2}

Decimal Notation

- 0.20710 \dots

Solution steps

sin (3 0^{\circ}) - cos (4 5^{\circ})

Use the following trivial identity:

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

sin (3 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{1}{2}

Use the following trivial identity:

cos (4 5^{\circ}) = \frac{2}{2}

cos (4 5^{\circ})

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{2}{2}

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

Simplify

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

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

Apply rule

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

= \frac{1 - 2}{2}

= \frac{1 - 2}{2}

\frac{6.47}{sec ( 2 0 ^{\circ} )}

tan (arctan (\frac{1}{3}))

cot (3 0^{\circ}) - sin (4 5^{\circ})

cos (2.2)

sec^{2} (4 0^{\circ})

What is the value of sin(30)-cos(45) ?
The value of sin(30)-cos(45) is (1-sqrt(2))/2