Question

Find the value of cos 15 ,using this result cos(a-b) = cosAcosB+sinAsinB

Answer 1

Step-by-step explanation:

if u want you can rationalise it later

Answer 2

Answer:

Step-by-step explanation:

LET A=60, B=45

NOW COS(A-B) =cosA cosB + sinA sinB

COS(60-45)=COS60*COS45+ SIN 60*SIN45

COS(15)=$\frac{1}{2} *\frac{1}{\sqrt{2} } +\frac{\sqrt{3} }{2}*\frac{1}{\sqrt{2} }$

cos(15)=$\frac{\sqrt{3} +1}{2\sqrt{2} }$

cos(15)=$\frac{\sqrt{6}+\sqrt{2} }{4}$ (on rationalising)

PLEASE MAK AS BRAINLIST ANSWER