How do you evaluate arcsin(22)?

1 Answer
May 24, 2015

sin(π4)=22 is the length of one side of the isoceles right angled triangle with sides 22, 22 and 1, which has internal angles π4, π4 and π2.

(π4 radians = 45o and π2 radians = 90o if you prefer)

To show this is right angled, check with Pythagoras:

(22)2+(22)2

=2222+2222

=24+24=12+12=1=12

So since sin(π4)=22 and π4 is in the

required range for arcsin viz π2θπ2, we find

arcsin(22)=π4