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"Calculate cos theta to two decimal places. (Use the pic attached inside!!!)

A. 0.61

B. 1.44

C. 0.72

D. 0.43

Calculate cos theta to two decimal places Use the pic attached inside A 061 B 144 C 072 D 043 class=

Respuesta :

Let
T = theta
Use the Law of Cosines to get
c^2 = a^2+b^2 - 2ab*cos(T)
7^2 = 10^2+8^2 - 2*10*8*cos(T)
49  = 164 - 160*cos(T)
-160cos(T) = 49-164
-160cos(T) = -115
cos(T) = -115/(-160)
cos(T) = 23/32
cos(T) = 0.71875 which rounds to 0.72

The final answer is C) 0.72
MissPhiladelphia
let teh greek symbol theta be equal to x. since the triangle is scalene, then apply law of cosine.

a2=b2 + c2 - 2cosx
let a = 7, b = 8 and c = 10

7^2 = 8^2 + 10^2 - 2(8)(10)cosx
cosx = 23/32 or 0.72
x = 44.05 degrees
 
the answer is letter C

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