Use a calculator to find the approximate value of cos-1(0.78).

38.74

Step-by-step explanation:

Hello, I think  I can help you with this.

in a standard calculator you will find the inverse cosine function as the second function of the cosine key

so

step 1

once the calculator is on, press the shift key and then the cosine key, then write the number and close the parenthesis, finally press the equal key

shift ⇒cos⇒0.78⇒)⇒=

in the display you will see( DEG mode)

Now, approximate

      38.7394246\≈38.74

Have a great day.

x² + 3x + 7 = 0       [ax² + bx + c]

a = 1

b = 3

c = 7

quadratic formula:

    (+/- is this ±)

plug in the numbers into the variables

your answer is a