What is the value of cos((7pi)/5) ?

The value of cos((7pi)/5) is -(sqrt(2)sqrt(3-\sqrt{5)})/4

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cos((7pi)/5)

cos (\frac{7 π}{5})

- \frac{2 3 - 5}{4}

Solution steps

cos (\frac{7 π}{5})

Rewrite using trig identities:

- sin (\frac{9 π}{10})

= - sin (\frac{9 π}{10})

Rewrite using trig identities:

sin (\frac{9 π}{10}) = \frac{2 3 - 5}{4}

= - \frac{2 3 - 5}{4}

tan (arcsin (\frac{7}{8}))

cos (37. 5^{\circ}) cos (7.5)

\frac{tan ( 14 0 ^{\circ} ) - tan ( 6 0 ^{\circ} )}{1 + tan ( 14 0 ^{\circ} ) tan ( 6 0 ^{\circ} )}

(sec (\frac{π}{4}))^{2}

arcsin (- \frac{5}{13})

What is the value of cos((7pi)/5) ?
The value of cos((7pi)/5) is -(sqrt(2)sqrt(3-\sqrt{5)})/4