Geometry

First one

The smallest angle is opposite the shortest side   and the largest angle is opposite the longest side

Using the Law of Sines......we have that

Sin 36           Sine of angle opposite longest side          

_____    =    ________________________

  53                         90

Multiply both sides by 90

90 Sine 36/53   = Sin of angle opposite the longest side......using the sine inverse, we have

arcsin [ (90/53)sin 36 ] =   sine of angle opposite the longest side ≈  86.5°

Second one....

Here's a YouTube video that explains this better than I can.....

https://www.youtube.com/watch?v=YEX2mhvbYuo

Last one :

Area of sector   GHJ  =

(1/2)  radius^2 *  measure of angle GHJ in radians.....so we have...

(1/2)  (5^2)   * pi /4  =

25 / 8  pi  cm^2   ≈   9.8 cm^2