Question

what is the value of cos 2a/sina+cosa​

Answer 1

Answer: cosa - sina

Explnanation:

We know, cos(A + B) = cosAcosB - sinAsinB

=> cos(a + a) = cosacosa - sinasina

=> cos2a = cos²a - sin²a = (cosa + sina)(cosa - sina)

Therefore,

cos2a/(sina + cosa) = (cosa + sina)(cosa - sina)/(sina + cosa) = cosa - sina.

More:

• sin(A + B) = sinAcosB + cosAsinB
• tan(A + B) = (tanA + tanB)/(1 - tanAtanB)
• cot(A + B) = (cotAcotB - 1)/(cotA + cotB).