Question

17. If sin A =1/2
prove that 3 cos A - 4 cos3 A = 0​

Answer 1

Answer:

sinA =1/2

so, we can write it as p/h

acc to Pythagoras theorem

(h) ²=b²+p²

2²=b² +1²

4-1=b²

b =√3

cosA=b/h

√3/2

put value in eqn

3(√3/2) -4=0

3√3/2-4=0

3√3-8/2=0

proved