Question

what is a formula sin 20​

Answer 1

Answer:

Call sin 20 = t. Apply the trig formula: sin3a=3sina−4sin3a. sin60=√32=3t−4t3. We get an equation of third deg in t = sin 20. 4t^3 - 3t + sqrt3/2 = 0.

Answer 2

Call sin 20 = t. Apply the trig formula: sin3a=3sina−4sin3a. sin60=√32=3t−4t3. We get an equation of third deg in t = sin 20. 4t^3 - 3t + sqrt3/2 = 0