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3 years ago

Cos s=-2/5 and sin t=4/5, s and t are in quadrant II find cos(s+t) and cos(s-t)

Mathematics

1 answer:

mojhsa [17]3 years ago

5 0

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

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Answer:

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Solution:

A family of 3 children and 2 adults visited a health club. The club charges $y an hour for each child and $x an hour for each adult.

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$(x_1,y_1)\ and\ (x_2,y_2)$

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