Question

If P Q and R are interior angles of a tringle Delta PQR then show that cos((Q+R)/(2))=sin(P)/(2)​

Answer 1

Answer:

Step-by-step explanation:

In triangle PQR,

angle P+  angle Q+ angle R= 180  [sum of all the angles in a triangle is 180 degrees]

P/2+ Q/2+ R/2= 90

Q/2+R/2=90-P/2

Multiplying both the sides by cos

cos Q/2+R/2 = cos (90-P/2)

cos Q+R/2 = cos (90-P/2)    [ sin Ф= cos 90-Ф]

cos Q+R/2 = sin P/2