Please someone help me..

 see proof below

Step-by-step explanation:

Use the Triple Angle Identity: sin 3A = 3sinA - 4sin³A

Proof LHS → RHS

LHS:                                 sin Ф

Let A = Ф/3                     sin 3A

Triple Angle Identity:     3sinA - 4sin³A

Substitute Ф/3 = A:         3sin(Ф/3) - 4sin³(Ф/3)

Substitute sin(Ф/3):        

rick has $1400 and sally has $1500

step-by-step explanation:

to find amount of money rick has after 10 years :

principal = $1000 , time = 10 years , rate = 4% annually

to find amount of money sally has after 10 years :

her friend gives to pay her $50 per year, therefore money she has after 10 years = 50 × 10 = $500

also, sally gets $1000 after 10 years,

therefore, total amount of money sally has after 10 years = 500 + 1000 = $1500

so, after 10 years : rick has $1400 and sally has $1500