What is the general solution for cos(x)=(-2)/5 ?

The general solution for cos(x)=(-2)/5 is x=1.98231…+2pin,x=-1.98231…+2pin

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cos(x)=(-2)/5

cos (x) = \frac{- 2}{5}

x = 1.98231 \dots + 2 πn, x = - 1.98231 \dots + 2 πn

Solution steps

cos (x) = \frac{- 2}{5}

Apply the fraction rule:

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

cos (x) = - \frac{2}{5}

Apply trig inverse properties

x = arccos (- \frac{2}{5}) + 2 πn, x = - arccos (- \frac{2}{5}) + 2 πn

Show solutions in decimal form

x = 1.98231 \dots + 2 πn, x = - 1.98231 \dots + 2 πn

sin (\frac{θ}{2}) = \frac{1}{m}

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

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

6 tan (x) = tan^{2} (x), x = 0

5 cos^{2} (x) + 3 cos (x) - 1 = 0

What is the general solution for cos(x)=(-2)/5 ?
The general solution for cos(x)=(-2)/5 is x=1.98231…+2pin,x=-1.98231…+2pin