Question

Using the formula cos(A+B) = cosAcosB - sinAsinB, find the value of sin75°

Answer 1

Answer:

$(sqrt{3 +1 ) / 2\sqrt{2}$

Step-by-step explanation:

Since sin 75 = cos 15 ,

Take A = 45 and B = -30

Now using the formula, cos(45-30) = cos45*cos(-30) - sin45*sin(-30) ;

cos15 =( $\sqrt{3} / 2\sqrt{2}$) -( $-1/2\sqrt{2}$) = $(sqrt{3 +1 ) / 2\sqrt{2}$