Question

cos x/3 = 1/√2 срочно

Answer 1

$cos \frac{x}{3} = \frac{1}{ \sqrt{2} }$
⇒$\frac{1}{ \sqrt{2} } = \frac{1}{ \sqrt{2} } *1= \frac{1}{ \sqrt{2} } * \frac{ \sqrt{2} }{ \sqrt{2} }= \frac{ \sqrt{2} }{2}$
⇒$\frac{x}{3} =+-arccos \frac{ \sqrt{2} }{2} +2 \pi k$
⇒$\frac{x}{3} =+- \frac{ \pi }{4}+2 \pi k$
⇒$x=+- \frac{3* \pi }{4} + 6 \pi *k;$ k∈Z

Answer 2

cos (x/3)= √2/2
x1/3= π/4+2πk1        k1∈z
x1= 3π/4 +6πk1       k1∈z

x2/3= 7π/4+ 2πk2     k2∈z
x2= 21π/4 +6πk2       k2∈z