
= (1/2) (17.2) (7.1) sin (21.67)
= 22.5470 square meters
The angle whose sine is 0.39581 is 23.31650126° (round it how you want).
To calculate this, you need to do the inverse sine of 0.39581.
Inverse sine looks like

, however, it is not the sine of the angle to the power of -1.
Given:
The recurring decimal is
.
To prove:
Algebraically that the recurring decimal
can be written as
.
Proof:
Let,


Multiply both sides by 100.
...(i)
Multiply both sides by 10.
...(ii)
Subtract (i) from (ii).


Divide both sides by 900.


So,
.
Hence proved.