Question

This is question
$if \: sin \alpha = 3 \5 \: where \: \pi \div 2 < \alpha < \pi \: evaluate \: cos3 \alpha \: and \: tan2 \alpha$
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Answer 1

Answer:

if sin alpha =3/5 then alpha =37°( remember the 3-4-5 triangle)

sin alpha =3/5

cos alpha =4/5 ( from identity)

Now apply the formula of cos 3alpha

similarly tan alpha =3/4

now apply formula of tan 2alpha