Any one be my friend​

Express the following as a function of a single angle, cos(60) cos(-20) - sin(60) sin(-20)

What values of x satisfy the inequality x^2-9x< 0? how is your answer shown on the graph?

1. ∠1 is complementary to ∠2 and ∠3 is complementary to ∠2. subtraction property of equality 2. m∠1 + m∠2 = 90 and m∠3 + m∠2 = 90 substitution 3. m∠1 + m∠2 = m∠3 + m∠2 definition of complementary 4. m∠1 = m∠3 given