I'm studying for Trigonometry exam but there are fews problems that involves Trig Identities that i don't know how to solve. Please help me solve these problems asap.

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a) 1 - sin x = cos^2x

b) cosx cos2x + 1/2 = sin2x sinx

c) cos x = sin2x

d) If a and b are second-quadrant angles such that sin a= 4/5 and tan= -12/5, find sin(a+b).

Thanks for your helps

my issue has been solved

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a) 1 - sin x = cos^2x

b) cosx cos2x + 1/2 = sin2x sinx

c) cos x = sin2x

d) If a and b are second-quadrant angles such that sin a= 4/5 and tan= -12/5, find sin(a+b).

Thanks for your helps

my issue has been solved

Last edited: