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Home > PC > Chapter 6 > Lesson 6.3.2 > Problem 6-130

6-130.

If , , find exact values for and .

Draw and label a circle with the reference angle in the correct quadrant.
Find the length of the unlabeled side.

Use the Double Angle Formula for the sine to find .

Circle with horizontal & vertical diamaters, point in third quadrant, right triangle, hypotenuse is radius from center to point, labeled 7, horizontal leg is on negative x axis, vertical leg labeled negative 3.

Use one of the Double Angle Formulas for the cosine to find .

Double - Angle Formulas: Sine


Double - Angle Formulas: Cosine
1.
2.
3.