Question

find the numerical value of sin3pi/2 +pi/4

Answer 1

Use trig identity: sin (a + b) = sin a*cos b* + sin b* cos a
y = sin (3Pi/2 + Pi/4) = sin 3Pi/2 cos Pi/4 + sin Pi/4*cos 3Pi/2
Since sin 3Pi/2 = -1; cos 3Pi/2 = 0; cos Pi/4 = V2/2, then,
y = (-1)*(V2/2) = -V2/2