Question

Sin a 12/13 a sudut lancip .tentukanlah si 2a ,cos 2a ,tan 2a

Answer 1

Sin A = 12/13 = y/r
x²+y² = r²
x² = r² - y²
x² = 13² -12²
x = 5

cos A = x/r = 5/13

a) sin 2A = 2 sin A cos A = 2(12/13)(5/13) = 120/13
b) cos 2A = 2cos² A -1 = 2(5/13)² -1 = 50/169 - 1 = - 119/169
c) tan 2A = sin 2A /.cos 2A = (120/13 ) : (-119/169) = -1.560/149 
tan 2A = - 10 ⁷⁰/₁₄₉