Question

WILL GIVE MEDAL AND FAN FOR HELP!!! Can someone please show me step by step how to do this problem?!? Picture attached below.

Answer 1

first we take (cosa) as a common factor

Answer 2

and then we will be having 2 probabilities
either cosa = 0
or cosa -1 =0

Answer 3

and by solving it we can find the values of A

Answer 4

\[cosA (\cos A -1)=0\]

Answer 5

did you get it ?

Answer 6

Else we can also get answer by choice verification since choice was given..
ny verifying choice time eill be saved and useful in competitive exams.

Answer 7

\[2cos^2(A)-cos(A)=0\]Lets call\[cos(A)=x\]\[2x^2-x=0\]\[x*(2x-1)=0\]Therefore\[x_1=0~~and~~x_2=\frac{1}{2}\]If x=0:\[cos(A)=0~~~~\therefore A=90^o\]If x=1/2 :\[cos(A)=\frac{1}{2}~~~~\therefore A=60^o\]Your answer is:\[S=\{60^o,90^o\}\]