Question

guys can you find the value of sin 20° like sin 30° = 1/2
$....$
If yes , how
$...$
If no , then don't answer
$...$
don't use calculator​

Answer 1

Step-by-step explanation:

see, there are 2 ways.

first, you can find the value by seeing the graph of sine.

secondly,

you can get it from sine value table....

one more thing, it's a suggestion:

not for sin 20, but for values like sin 15, sin 7.5 etc you can calculate by following formula:

$\sin( \alpha + \beta ) = \sin( \alpha ) \cos( \beta ) + \sin( \beta ) \cos( \alpha )$

e. g suppose you need to calculate sin 15

what you'll do is

take some known value, suppose sin 45

it can be written as

sin(30+15), by using the above formula, you can write it as

sin(30+15)=sin30cos15+sin15 cos30

(1/√2)=(1/2)cos15 + (√3/2)(sin15)......(1)

secondly

sin(60-15)=sin60cos15-sin15cos60

(1/√2)=(√3/2)cos15-sin15(1/2).......(2)

solve (1) and (2), you'll get value of sin15