Posted by Anonymous on .
use an appropriate halfangle formula to find the exact value ofthe expression.
tan22.5
write the product as a sum
sinxsin5x
write the sum as a product
sin2xsin7x

pre calc 
JQuiroz,
sinxsin5x
sinucosv= 1/2[cos(uv)cos(u+v)]
= 1/2[cos(x5x)cos(x+5x)]
= 1/2[cos(4x)cos(6x)]
= 1/2cos4x1/2cos6x