If ΞΈ is an acute angle and sin ΞΈ = (2β7) / 7, use the identity sinΒ²ΞΈ + cosΒ²ΞΈ = 1 to find cos ΞΈ.

In Exercises 21β28, convert each angle in radians to degrees. -3π
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Radian Measure
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Conversion between Radians and Degrees
In Exercises 28β29, find a cofunction with the same value as the given expression. sin 70Β°
In Exercises 25β32, the unit circle has been divided into eight equal arcs, corresponding to t-values of 0, π, π, 3π, π, 5π, 3π, 7π, and 2π. 4 2 4 4 2 4 a. Use the (x,y) coordinates in the figure to find the value of the trigonometric function. b. Use periodic properties and your answer from part (a) to find the value of the same trigonometric function at the indicated real number.
cos 9π/2
In Exercises 23β34, find the exact value of each of the remaining trigonometric functions of ΞΈ. cos ΞΈ = 8/17, 270Β° < ΞΈ < 360Β°
In Exercises 25β30, use an identity to find the value of each expression. Do not use a calculator. sinΒ² π + cosΒ² π 10 10
In Exercises 25β32, the unit circle has been divided into eight equal arcs, corresponding to t-values of
0, π, π, 3π, π, 5π, 3π, 7π, and 2π.
4 2 4 4 2 4
a. Use the (x,y) coordinates in the figure to find the value of the trigonometric function.
cos 3π/4
