Question

pls help urgent help needed

Answer 1

for Q.a
use the identity :
cosAcosB + sinAsinB = cos(A-B)

Answer 2

what u get ?

Answer 3

i got 24 which is right

Answer 4

@RadEn

Answer 5

yes, it is cos24

Answer 6

for Q.b
use the identity :
sinAcosB - cosAsinB = sin(A-B),
multiply by -1 to both sides, giving us
cosAsinB - sinAcosB = - sin(A-B)

Answer 7

in this case, given A = 17 and B = 7

Answer 8

for b will the answer be -10

Answer 9

hmmm....
cosAsinB - sinAcosB = - sin(A-B)
put A= 17 and B=7
cos17sin7 - sin17cos7 = - sin(17-7)
cos17sin7 - sin17cos7 = - sin10

then use the identity :
-sinx = sin(-x)

so, we get -sin10 = sin(-10)

you were right :)

Answer 10

and how do we do part 3 i got the wrong answer for it just have once chance left on it

Answer 11

do like Q.b for Q.c
i think u can solve this, now :)

Answer 12

@RadEn i got the wrong answer again for part 3

Answer 13

hmmm..
cos3sin(-2) - cos2sin3
= -cos3sin2 - cos2sin3
= - {cos3sin2 + cos2sin3}

we have to use the identity
cosAsinB + cosBsinA = sin(A+B)

so,
- {cos3sin2 + cos2sin3}
= - sin(3+2)
= -sin5

again, use the identity
-sinx =sinx

now we have
-sin5 = sin(-5)

Answer 14

thanks @RadEn