Question

if cos a=12/13 find the value of sin 3a​

Answer 1

Answer:

sinA =5/13

sin 3A=3 sinA-4sin³A

=3×5/13- 4×(5/13)³

=15/13- 4×125/2197

=15/13- 500/2197

=2535-500/1927

=2035/1927

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