diff --git a/src/trig.jl b/src/trig.jl
index 356d616..77214c1 100644
--- a/src/trig.jl
+++ b/src/trig.jl
@@ -85,7 +85,7 @@ function cos_main(X::IntervalBox)
 end
 
 # TODO: Be careful with the pi constants if using e.g. BigFloats
-cos_reverse = symmetrise(cos_main, reflect_x(0.0))
+cos_reverse = symmetrise(cos_main, reflect_x(zero))
 
 """
     cos!(X::IntervalBox)
@@ -128,7 +128,7 @@ function tan_main(X::IntervalBox)
 
     x, y = X
 
-    h = sup(half_pi)
+    h = sup(half_pi(x))
 
     x_range = _build_interval(x, -h, h)
 
@@ -143,7 +143,7 @@ function tan_main(X::IntervalBox)
 
 end
 
-tan!(X::IntervalBox) = periodise(tan_main, interval(π))(X)
+tan!(X::IntervalBox) = periodise(tan_main, pi_interval)(X)
 
 """
     tan_rev(c::IntervalType[, x::IntervalType])
diff --git a/test/runtests.jl b/test/runtests.jl
index 90e3932..88c77e7 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -2,6 +2,8 @@ using IntervalContractors
 using IntervalArithmetic
 using Test
 
+using IntervalContractors: IntervalType
+
 # cache current power mode:
 orig_power_mode = IntervalArithmetic.power_mode()
 
@@ -37,7 +39,8 @@ approx_eq(x::IntervalType, y::IntervalType) =
     end
 
     @testset "Exponents with integer values but not types" begin
-        @test all(eq.(power_rev(entireinterval(), -interval(4, 4), 2.0),  (entireinterval(), interval(-4, -4), 2.0)))
+        @test eq(power_rev(entireinterval(), interval(-4, 4), interval(2.0)),
+                (entireinterval(), interval(-4, 4), interval(2.0)))
     end
 end