Multiples And Sub-Multiples
We know
sin3A=3 sinA - 4 sin3A
Put A =\(
\frac{A}
{3}
\)
sinA = 3sin\( \frac{A} {3} \) - 4sin3\( \frac{A} {3} \) (xiii)
We know
cos3A = 4 cos3A - 3cosA
put A = \(
\frac{A}
{3}
\)
cosA =4 cos3\(
\frac{A}
{3}
\) - 3 cos\(
\frac{A}
{3}
\) (xiv)
We know, tan 3A =\(
\frac{{3\tan A - \tan ^3 A}}
{{1 - 3\tan ^2 A}}
\)
put \(
A = \frac{A}
{3}
\)
\(
\tan A = \frac{{3\tan \frac{A}
{3} - \tan ^3 \frac{A}
{3}}}
{{1 - 3\tan ^2 \frac{A}
{3}}}\,\,\,\,\, \to (xv)
\)
we know
\(
\cot 3A = \frac{{3\cot A - \cot ^3 A}}
{{1 - 3\cot ^2 A}}
\)
put A = \(
\frac{A}
{3}
\)
\(
\cot A = \frac{{3\cot \frac{A}
{3} - \cot ^3 \frac{A}
{3}}}
{{1 - 3\cot ^2 \frac{A}
{3}}}\,\,\,\,\, \to (xvi)
\)