Find the exact value.

Find $\mathrm{cos}2\theta $

y=20 r=29 x=21

Find $\mathrm{cos}2\theta $

y=20 r=29 x=21

Darryl English
2022-07-26
Answered

Find the exact value.

Find $\mathrm{cos}2\theta $

y=20 r=29 x=21

Find $\mathrm{cos}2\theta $

y=20 r=29 x=21

You can still ask an expert for help

Tamoni5e

Answered 2022-07-27
Author has **14** answers

$\theta =\mathrm{cos}-1(21/29)$

Trig identity:

$\mathrm{cos}2\theta =2\mathrm{cos}2(\theta )-1$

$2{\mathrm{cos}}^{2}({\mathrm{cos}}^{-1}(21/29))-1=2(21/29{)}^{2}-1=41/841$

Trig identity:

$\mathrm{cos}2\theta =2\mathrm{cos}2(\theta )-1$

$2{\mathrm{cos}}^{2}({\mathrm{cos}}^{-1}(21/29))-1=2(21/29{)}^{2}-1=41/841$

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I thought that this minor inequality should help

which is true.

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