Nilai cos2 π/6 sin2 5π/6 + cos 3π/5 sin π/4

[tex]\displaystyle \cos^2\frac16\pi\cdot\sin^2\frac56\pi+\cos\frac35\pi\sin\frac14\pi=\left(\frac12\sqrt3\cdot\frac12\right)^2+\left(\frac{1+\sqrt5}{4}\right)\left(\frac1{2}\sqrt2\right)\\\boxed{\boxed{\cos^2\frac16\pi\cdot\sin^2\frac56\pi+\cos\frac35\pi\sin\frac14\pi=\frac3{16}+\frac{1}{8}\sqrt2+\frac{1}{8}\sqrt{10}}}[/tex]