Question

Sam used his calculator to find cos 1.75. he wrote down cos 1.75 = .999. how could sam recognize that his answer is incorrect?

Answer 1

Explanation:

Since π=3.14 and 1.75 should be half of π so cos(1.75) should be in the approximation of
`(√(2))/(2)` or
`0.7`.

Clearly Sam's calculator is in the degree mode since
`cos(1.75^(\circ))`

is about
`.999` and obviously,
`\frac{{\pi}}{2}<1.75<{\pi}`, So on the unit circle, it will be in the second quadrant.

Thus, cos(1.75) is negative.