Question

Prove that :

${sin}^{2} \binom{\pi}{18} + \: {sin}^{2} \binom{\pi}{9} + {sin}^{2} \binom{7\pi}{18} + {sin}^{2} \binom{4\pi}{9 } \: \: = \: \: 2$


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Answer 1

Step-by-step explanation:

just subtract the angle in 3rd and 4th from

$\frac{\pi}{2 }$

then use

$\sin ^{2} (x) + \cos ^{2} ( x) = 1$