What is the general solution for cos(a)=-4/5 ?

The general solution for cos(a)=-4/5 is a=2.49809…+2pin,a=-2.49809…+2pin

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cos(a)=-4/5

cos (a) = - \frac{4}{5}

a = 2.49809 \dots + 2 πn, a = - 2.49809 \dots + 2 πn

Solution steps

cos (a) = - \frac{4}{5}

Apply trig inverse properties

a = arccos (- \frac{4}{5}) + 2 πn, a = - arccos (- \frac{4}{5}) + 2 πn

Show solutions in decimal form

a = 2.49809 \dots + 2 πn, a = - 2.49809 \dots + 2 πn

2 tan (θ) - sec (θ) = 0

sin (θ) = \frac{175}{214}

2 \cdot cos^{2} (x) - cos (x) - 1 = 0, 0 \leq x \leq π

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

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

What is the general solution for cos(a)=-4/5 ?
The general solution for cos(a)=-4/5 is a=2.49809…+2pin,a=-2.49809…+2pin