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

The general solution for cos(x)= 2/5 is x=1.15927…+2pin,x=2pi-1.15927…+2pin

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cos(x)= 2/5

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

x = 1.15927 \dots + 2 πn, x = 2 π - 1.15927 \dots + 2 πn

Solution steps

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

Apply trig inverse properties

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

Show solutions in decimal form

x = 1.15927 \dots + 2 πn, x = 2 π - 1.15927 \dots + 2 πn

sin (θ) + cos (θ) = 2

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

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

sec (3 x) = \frac{2}{3}, 0 \leq x \leq 2 π

sec (4 x) - 2 = 0

What is the general solution for cos(x)= 2/5 ?
The general solution for cos(x)= 2/5 is x=1.15927…+2pin,x=2pi-1.15927…+2pin