Cosa cos2a cos4a cos8a=sin16a/16sina

You can use the result here:

link

This identity suggests that

From here, you can use the sum/difference identities for cosine.

Apply these carefully to the right hand side and it should reduce quite nicely to the same expression on the left.

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

you save $70

discount would be 35% off

step-by-step explanation: