The solution set of sin2θ=−12 is
{nπ2+(−1)n+1π6:n∈Z}
{nπ2+(−1)nπ12:n∈Z}
{nπ3+(−1)n2π15:n∈Z}
{nπ2+(−1)n+1π8:n∈Z}
sin2θ=−12=sin-π4⇒2θ=nπ+-1n-π4 ⇒θ=nπ2+-1n+1π8