Question

the value of sin 20, sin 40, sin 80 and sin 90 is​

Answer 1

$\huge\bold\color{blue}{\boxed{Question}}$

What is the value of Sin 20 + sin 40 - sin 80?

$\huge\bold\color{red}{\boxed{☆Answer ☆}}$

= Sin 20 + Sin 40 - Sin 80

= Sin 20 + Sin 40 - Sin ( 60 + 20 )

= Sin 20 + Sin 40 - ( Sin 60 * Cos 20 + Cos 60 * Sin 20 )

( Applied formula

●Sin ( A + B ) = Sin A * Cos B + Cos B * Sin A

●S + S = 2*S*C. )

Now,

= 2 * Sin 60 * Cos 20 - Sin60 * Cos20 - Cos60 * Sin20

= Sin 60 * Cos 20 - Cos60 * Sin 20

= Sin ( 60 - 20 )

= Sin 40

So the ans is Sin 40.

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I hope it will help you....