Question

if sec^2 a+tan^2 a=9 find sin a​

Answer 1

sec²a+tan²a=9

1/ cos²a+sin²a/cos²a=9

(1+sin²a)/cos²a=9

1+sin²a=9cos²a

1+sin²a=9(1-sin²a)

1+sin²a=9-9sin²a

10sin²a=8

sin²a=8/10=4/5

sinA= √(4/5)= 2/√5