How do you find sin^-1(sin ((5pi)/6))sin1(sin(5π6))?

2 Answers
Mar 27, 2018

sin^-1(sin(5pi)/6)=pi/6sin1(sin(5π)6)=π6

Explanation:

sin((5pi)/6)=1/2sin(5π6)=12, so we're really being asked for sin^-1(1/2).sin1(12).

Let

y=sin^-1(1/2)y=sin1(12)

Then, from the definition of arcsine,

1/2=sin(y)12=sin(y)

( y=sin^-1(a) hArr a=sin(y)y=sin1(a)a=sin(y) )

In other words, we want to know where the sine function returns 1/2.12.

Sine is equal to 1/212 for pi/6+2npi, (5pi)/6+2npi,π6+2nπ,5π6+2nπ, where nn is any integer. But really, since the domain of arcsine is [-pi/2, pi/2], pi/6[π2,π2],π6 is the only valid answer.

Mar 27, 2018

pi/6π6

Explanation:

Hint:
We know that ,
color(red)(sin^-1(sintheta)=theta,sin1(sinθ)=θ, where, color(red)(theta in [-pi/2,pi/2]θ[π2,π2]
Even though,
color(blue)(sin^-1(sin((5pi)/6))!=((5pi)/6),sin1(sin(5π6))(5π6), because, color(blue)((5pi)/6 !in [-pi/2,pi/2]5π6[π2,π2]
So, we reduce theta=(5pi)/6.θ=5π6. But how ? By using Addition and Subtraction Formulas for sine and cosine .Now enjoy the answer.

****Answer:****

Here,

(5pi)/6=pi-pi/65π6=ππ6

(sin^-1(sin((5pi)/6))=sin^-1(sin(pi-pi/6))(sin1(sin(5π6))=sin1(sin(ππ6))

=sin^-1(sin(pi/6))....to, Apply color(red)([sin(pi-theta)=sintheta ]

=pi/6......to, where, pi/6in[-pi/2,pi/2]