1 thought on “50. If sin2A = 2sinAcosA and sin20° = K, then the value of cos20° cos40° cos80° cos160º =”
Step-by-step explanation:
cos20×cos40×cos80×cos160mulitply and divide by sin20sin20sin20cos20×cos40×cos80×cos160as sin20cos20=12×sin40sin40×cos40×cos80×cos1602×sin20again sin40×cos40=sin802=sin80×cos80×cos16022×sin20=sin160×cos16023×sin20=sin32024×sin20=sin(360−40)24×sin20=−sin(40)24×sin20=−2sin20×cos2024×sin20=−cos208use cosθ=1−sin2θ−−−−−−−−√=−1−k2√8Thereforecos20×cos40×cos80×cos160=−
Step-by-step explanation:
cos20×cos40×cos80×cos160mulitply and divide by sin20sin20sin20cos20×cos40×cos80×cos160as sin20cos20=12×sin40sin40×cos40×cos80×cos1602×sin20again sin40×cos40=sin802=sin80×cos80×cos16022×sin20=sin160×cos16023×sin20=sin32024×sin20=sin(360−40)24×sin20=−sin(40)24×sin20=−2sin20×cos2024×sin20=−cos208use cosθ=1−sin2θ−−−−−−−−√=−1−k2√8Thereforecos20×cos40×cos80×cos160=−