Loonie

Loonie has three wooden sticks measuring 17 inches, 21 inches, and 25 inches. He lays them down to form a triangle. Find the measure of the angle enclosed by 17 inches and 21 inches. (Express answers to the nearest hundredths) (using the law of cosines)

Correct answer:

γ =  81.5435 °

Step-by-step explanation:

a=17 in b=21 in c=25 in  c2=a2+b22 a b cosγ  2 a b cosγ=a2+b2c2  k=cosγ  k=2 a ba2+b2c2=2 17 21172+212252=3450.1471  γ=π180°arccosk=π180°arccos0.1471=81.5435=81°3237"

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