Question

Find the exact value of sin ( 2

a. if cos a = 3 /5 . assume a is a quadrant i angle in standard position.

Answer 1

In a right angled triangle 'efg' cos a = 3/5
From Pythagoras theorem the third side will be 4
cos a =3/5
sin a =4/5
sin 2a =2 x 4/5
sin 2a= 8/5