The correct answer is D, 146 inches.
7 x 12 = 84
4 x 12 = 48
84+48+4+10 = 146
- cos ( 1/2 x + 1/5 π ) = 0 ( and because if cos α = 0, α= π/2 + k π, k ∈ Z )
1/2 x + π/5 = π/2 + k π, k ∈ Z
1/2 x = π/2 - π/5 + k π / * 2
x = π - 2π/5 + 2 k π
x = 3/5 π + 2 k π = 0.6 π + 2 k π
Answer:
If k = 0: x 1 = 0.6 π = 3π/5
k = 1 : x 2 = 2.6 π = 13π/5
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