Question 1152666
If 
{{{sin^2(pi/9) + sin^2(2pi/9) + sin^2(3pi/9) + sin^2(4pi/9) = 9/4}}}, 

evaluate {{{cos^2(pi/9) + cos^2(2pi/9) + cos^2(3pi/9) + cos^2(4pi/9)}}}
<pre>
{{{cos^2(pi/9) + cos^2(2pi/9) + cos^2(3pi/9) + cos^2(4pi/9)=""}}}

{{{(1-sin^2(pi/9)^"") + (1-sin^2(2pi/9)^"") + (1-sin^2(3pi/9)^"") + (1-sin^2(4pi/9)^"") = ""}}}

{{{1-sin^2(pi/9) + 1-sin^2(2pi/9) + 1-sin^2(3pi/9) + 1-sin^2(4pi/9) = ""}}}

{{{4-sin^2(pi/9)-sin^2(2pi/9)-sin^2(3pi/9)-sin^2(4pi/9) = ""}}}

{{{4-(sin^2(pi/9)^""+sin^2(2pi/9)+sin^2(3pi/9)+sin^2(4pi/9)) = ""}}}

{{{4-9/4=""}}}

{{{16/4-9/4=""}}}

{{{7/4}}}

Edwin</pre>