Question

Find exact value of cos

Answer 1

√91/10

Explanation:

sin 0.3 is equal to 18(approximate value)

cos18°=0.951

which is √91/10

Answer 2

Answer: Choice B.
`(√(91))/(10)`

Work Shown:

`\sin^2 \theta + \cos^2 \theta = 1\\\\\left((3)/(10)\right)^2 + \cos^2 \theta = 1\\\\(9)/(100) + \cos^2 \theta = 1\\\\\cos^2 \theta = 1 - (9)/(100)\\\\\cos^2 \theta = (100)/(100)-(9)/(100)\\\\\cos^2 \theta = (91)/(100)\\\\\cos \theta = \sqrt{(91)/(100)} \ \text{ cosine positive in Q1}\\\\\cos \theta = (√(91))/(√(100))\\\\\cos \theta = (√(91))/(10)\\\\`