The one and the negative one
The method used is Distributive Property.
<h3>What is Distributive property?</h3>
The Distributive Property is an algebraic property that is used to multiply a single value and two or more values within a set of parenthesis.
Given:
(2x² - 1)(3x+2) = (2x²)(3x) + (2x²)(2) + (-1)(3x)+(-1)(2)
Here the property used is Distributive property.
Because distributive property in this way
a*(b+c)= a*b+ a*c
This is how a is being multiplied by with b and c.
Learn more about this Distributive property here:
brainly.com/question/4136433
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Answer:
•cos(s+t) = cos(s)cos(t) - sin(s)sin(t) = (-⅖).(-⅗) - (√21 /5).(⅘) = +6/25 - 4√21 /25 = (6-4√21)/25
•cos(s-t) = cos(s)cos(t) + sin(s)sin(t) = (-⅖).(-⅗) + (√21 /5).(⅘) = +6/25 + 4√21 /25 = (6+4√21)/25
cos(t) = ±√(1 - sin²(t)) → -√(1 - sin²(t)) = -√(1 - (⅘)²) = -⅗
sin(s) = ±√(1 - cos²(s)) → +√(1- cos²(s)) = +√(1 - (-⅖)²) = √21 /5
0.041 + 0.004
= 0.045
= 45/1000
