What is the general solution for cos(x)=(-1)/(sqrt(2)) ?

The general solution for cos(x)=(-1)/(sqrt(2)) is x=(3pi)/4+2pin,x=(5pi)/4+2pin

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cos(x)=(-1)/(sqrt(2))

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

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

Solution steps

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

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}

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

General solutions for

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

cos (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} cos (x) 1 \frac{3}{2} \frac{2}{2} \frac{1}{2} 0 - \frac{1}{2} - \frac{2}{2} - \frac{3}{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} cos (x) - 1 - \frac{3}{2} - \frac{2}{2} - \frac{1}{2} 0 \frac{1}{2} \frac{2}{2} \frac{3}{2}

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

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

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

y, cos (y) = x

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

1 + sin (x) = cos (x)

cos (2 x) = \frac{2}{π}

What is the general solution for cos(x)=(-1)/(sqrt(2)) ?
The general solution for cos(x)=(-1)/(sqrt(2)) is x=(3pi)/4+2pin,x=(5pi)/4+2pin