square square Calculate the value of cosalpha if sinalpha =-0,8 and 270^circ lt alpha lt 360^circ

To find the value of given that and , we can use the Pythagorean identity for trigonometric functions.The Pythagorean identity states that for any angle , the following equation holds: Given that , we can substitute this value into the equation: Simplifying the equation, we get: Subtracting 0.64 from both sides, we have: Taking the square root of both sides, we get: Since the angle is in the fourth quadrant ( ), the cosine function is positive in this quadrant. Therefore, the value of is: So, the value of is 0.6.