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

Question

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

anonymous · Answer

attachment

anonymous · Answer

first we take (cosa) as a common factor

anonymous · Answer

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

anonymous · Answer

and by solving it we can find the values of A

anonymous · Answer

$$cosA (\cos A -1)=0$$

anonymous · Answer

did you get it ?

anonymous · Answer

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.

anonymous · Answer

$$2cos^2(A)-cos(A)=0$$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:$$S=\{60^o,90^o\}$$