cos^2a/2=1-81/41^2=1600/41^2cosa/2=40/41sina=2*40*9/41^2=720/1681cosa=(1600-81)/41^2=1519/41^2tga=720/1519.
cos^2a/2=1-81/41^2=1600/41^2
cosa/2=40/41
sina=2*40*9/41^2=720/1681
cosa=(1600-81)/41^2=1519/41^2
tga=720/1519.