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WARRIOR [948]
3 years ago
15

Solve the equation sin x + cos x=cos 2x for 0 27. x

Mathematics
1 answer:
vodka [1.7K]3 years ago
8 0

Answer:

x=\frac{\pi}{4} and x=-\frac{3\pi}{4}

Step-by-step explanation:

We are given that sin x+cos x=cos 2x

We have to solve the given equation for 0\leq x\leq 2\pi

sin x+cos x=cos^2x-sin^2x

Because cos 2x=cos^2-sin^2

sinx+cos x=(sinx +cos x)(sinx-cos x)

1 =sin x-cos x

sin x=cos x

\frac{sinx }{cos x}=1

tan x=1

tan x=\frac{sinx}{cos x}

tan x=tan\frac{\pi}{4}

x=\frac{\pi}{4}

Tan x is positive in I and III quadrant

In III quadrant angle\theta  replace by \theta -\pi

Therefore, tan x=tan (\frac{\pi}{4}-\pi)=tan\frac{\pi-4\pi}{4}=tan\frac{-3\pi}{4}

x=-\frac{3\pi}{4}

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