Trig question (1 Viewer)

[VenomP]

If sin a = 3/4,
0 < a <pi/2 and sin b = 2/3, pi/2 < b < pi find the exact values of:

i. tan 2a
ii. cos (a - b)

screw it, the question wont post properly

 

[Timothy.Siu]

If sin a = 3/4, 0<a<pi/2 and sin b = 2/3, pi/2<b<pi

find the exact values of:

i. tan 2a
ii. cos (a - b)

tan 2a=2tana/(1-tan^2 a)
tan a=3/root7 (u can draw a triangle)
tan 2a=(6/root7)/ (1-9/7) (simplify)

ii. cos (a-b)=cos a cos b+sin a sinb
b is in the second quadrant.
cos a=root7/4 (draw a triangle)
cos b=-root5/3 (second quadrant so its negative)
sin a=3/4
sin b=2/3
sub them in.