rsin−1x=a,rcos−1x=b,rtan−1y=cSo, a+b=2rπ
cos(a+bπc)=cos(2rπrπtan−1y)
=cos(2tan−1y), let tan−1y=θ
=cos(2θ)
=1+tan2θ1−tan2θ=1+y21−y2
If asin−1x=bcos−1x=ctan−1y;0<x<1, then the value of cos(a+bπc) is:
Held on 26 Feb 2021 · Verified 6 Jul 2026.
1+y21−y2
1−y2
yy1−y2
2y1−y2
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