Question #122b2

1 Answer
Nov 28, 2016

24/252425

Explanation:

Use the trig identity:
sin (a + b) = sin a.cos b + sin b.cos a
In this formula, we know sin a and sin b.
We must find cos a and cos b.
sin a = 3/5 sina=35--> cos^2 a = 1 - 9/25 = 16/25cos2a=1925=1625 --> cos a = 4/5 cosa=45(because a is in Quadrant I)
sin b = 4/5sinb=45 --> cos^2 b = 1 - 16/25 = 9/25 cos2b=11625=925--> cos b = 3/5 cosb=35(Quadrant 1)
Finally,
sin (a + b) = (3/5)(4/5) + (3/5)(4/5) = 2(3/5)(4/5) = 24/25 sin(a+b)=(35)(45)+(35)(45)=2(35)(45)=2425