Question

if sin theta =4/5 then find the value of 3 sec theta -5 cos theta

Answer 1

As sin teta=4/5

cos teta=3/5 and sec teta=5/3

Hence, 3sec teta-5cos teta=3*5/3 - 5*3/5

=5-3

=2

Answer 2

sin A =4/5.

cos A=√(1-sin^2 A)

cosA = √(1 - (4/5)^2)

cos A = √ (1-16/25)

cos A = √(9/25)

cosA =3/5

sec A= 1 / cos A

secA = 5/3
so now ,

3 secA - 5cos A

=3 ×5/3 - 5×3/5

=15/3 -15/5

=5-3
=2.
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