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-BARSIC- [3]
3 years ago
10

5cosx -2sin(x/2) +7=0Help me to find x step by steppls​

Mathematics
1 answer:
miskamm [114]3 years ago
8 0

Answer:

x = 180

Step-by-step explanation:

First, you need to know

1. Double-angle formula:

cos(2x) = cos^{2}x - sin^{2}x

2. Pythagorean identity:

cos^{2}x + sin^{2}x = 1

Back to your problem, replacing the variable by the above:

5cosx-sin\frac{x}{2}+7 = 0

5(cos^{2}\frac{x}{2}-sin^{2}\frac{x}{2}) - 2sin\frac{x}{2} + 7 = 0 By Double-angle formula

5(1 - 2sin^{2}\frac{x}{2}) - 2sin\frac{x}{2} + 7 = 0 By Pythagorean identity

Given y = \frac{x}{2}

5(1-2sin^{2}y) - 2siny + 7 = 0

10sin^{2}y+2siny-12=0

5sin^{2}y+siny-6=0

(5siny + 6)(siny - 1)=0, we know -1 < sinx < 1, for every x ∈ R

siny = 1, y =90

y = \frac{x}{2}

x = 180

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