How to apply the sum of angles with the sine of an angle not on unit circle

The video tutorial explains how to find the sine and cosine of angles using trigonometric identities and the Pythagorean theorem. It focuses on angles in Quadrant 3, where both sine and cosine are negative. The tutorial demonstrates how to use triangles to calculate missing trigonometric values and simplify expressions. The process involves understanding the properties of Quadrant 3, applying the Pythagorean theorem, and using given values to find unknowns.

What is the given value for sine of U?

• -4/5

• -7/25

• 4/5

• 7/25

In which quadrant are the triangles drawn?

• Quadrant 2

• Quadrant 1

• Quadrant 3

• Quadrant 4

Why are both sine and cosine negative in Quadrant 3?

• Because x is positive and y is negative

• Because both x and y coordinates are positive

• Because x is negative and y is positive

• Because both x and y coordinates are negative

What theorem is used to find the missing side of the triangle?

• Sine rule

• Pythagorean theorem

• Tangent rule

• Cosine rule

What is the calculated value for the missing side using the Pythagorean theorem?

• 44

• 34

• 24

• 14

What is the final result after plugging in the values into the formula?

• 1/5

• 3/5

• 4/5

• 2/5

Which trigonometric identity is used in the final calculation?

• Cotangent addition formula

• Tangent addition formula

• Cosine addition formula

• Sine addition formula