Question

1. sin^2(x-1) / cos x =-1 find cos x

2. if alpha and beta are the measures of two first quadrant angles and sin alpha= 4/5 and sin beta= 5/13 find sin(alpha+beta)

Answer 1

\[\frac{ \sin ^{2}x-1 }{\cos x }=-1,\frac{ 1-\cos ^{2}x -1 }{\cos x }=-1\]
\[\cos x=1=\cos 0,x=0\]

Answer 2

so cos x=1

Answer 3

@RadEn @campbell_st @agent0smith

Answer 4

now you substitute in the formula sin (a+b)=sina cosb +cos a sin b

Answer 5

but how about the first one is the answer cos x =1

Answer 6

@surjithayer

Answer 7

im so lost right now

Answer 8

i have already solved it.
solve upto cosx=1 only

Answer 9

okay how did u sit up the equation for #2
@surjithayer

Answer 10

For 2 use the angle sum formula

Answer 11

it is an identity
\[\sin \left( \alpha+\beta \right)=\sin \alpha \cos \beta+\cos \alpha \sin \beta \]
you can also use \[\cos \left( \alpha+\beta \right)=\cos \alpha \cos \beta-\sin \alpha \sin \beta \]
then \[\sin \left( \alpha+\beta \right)=\sqrt{1-\cos ^{2}\left( \alpha+\beta \right)}\]

Answer 12

You'll also need to draw a triangle to find cos alpha and cos beta

Answer 13

.9998?? @surjithayer

Answer 14

No, keep exact numbers