Question

Please help! Geometry? ASAP

Given sinx=0.9 , what is cosx ?

Enter your answer as a decimal in the box. Round only your final answer to the nearest hundredth.

Answer 1

Approximately 0.44

Explanation:

There are two ways I can think of to solve this.

`sin^2+cos^2=1 rarr` It is like the Pythagorean theorem; they will add up to the hypotenuse squared (think of sin 90 (sin of hypotenuse), which is 1, sin x plus cos x is the sum of the sines of each of the non-right angles).

Plug the sin (0.9) in and solve for cosine

`0.9^2+cos^2=1`

`0.81+cos^2=1`

`cos^2=0.19`

`cos~~0.44 rarr` The square root of 0.19 could also be negative, but since the negative answer could not add up with `0.81` to equal 1, the answer must be positive.

Another way to solve this would be to put `sin^-1(9/10)` into your calculator. The answer will be the measure of angle x. Then plug the angle x (approximately 64.16) into the cosine function. The answer is also roughly 0.44.