$$\sec^2 x - 3 \sec x + 2 = 0$$
$$=$$> Â $$\sec^2x-2\sec x-\sec x+2=0$$
$$=$$> Â $$\sec x\left(\sec x-2\right)-1\left(\sec x-2\right)=0$$
$$=$$> Â $$\left(\sec x-2\right)\left(\sec x-1\right)=0$$
$$=$$>  $$\sec x-2=0$$ or  $$\sec x-1=0$$
$$=$$>  $$\sec x=2$$  or   $$\sec x=1$$
$$=$$>   $$\cos x=\frac{1}{2}$$  or   $$\cos x=1$$
$$=$$>   $$\cos x=\cos60^{\circ\ }$$  or   $$\cos x=\cos90^{\circ\ }$$
$$=$$>   $$x=60^{\circ\ }$$  or   $$x=90^{\circ\ }$$
Since  $$(0 < x < 90^\circ)$$
$$\therefore\ $$ $$x=60^{\circ\ }$$
Hence, the correct answer is Option C
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