# Pre Calculus

posted by Jessica Maths

Use the sum-to-product formulas to find the exact value of the given expression.

sin 150° + sin 30°

1. Jessica Maths

Sorry, I have figured out this one but cannot figure out this one

Use the sum-to-product formulas to write the given expression as a product. sin 4θ − sin 2θ

2. Reiny

sum of sines:
sinA + sinB = 2sin( (A+B)/2) cos( (A-B)/2)
then:
sin 150° + sin 30° = 2sin 90° cos 60°
= 2(1)(1/2)
= 1

Difference of sines:

sinA - sinB = 2cos( (A+B)/2) sin( (A-B)/2)

then:
sin 4θ − sin 2θ
= 2cos(3Ø)sin Ø

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